This is an article I submitted to the last Alternate GURPS issue of Pyramid. Since it did not make the cut and I wont be able to resubmit it I post it here in hopes some people get some use out of it.
There is one section of the article I am leaving out as I might be able to submit it for something later.
By Rory Fansler
Carlos mentally reached for the nearest Ley line and was rewarded with a surge of power that blurred his vision and staggered him. A moment later, he reached again and found enough power to lift his car out of the swamp. His happiness over not waiting for a tow truck almost erased his chagrin at missing the turn in the first place…
The existing Magery advantage is largely a holdover from earlier GURPS editions. What might it have looked like if it was created from scratch for the Fourth Edition? This article explores ideas about breaking that up into components so different styles can be modeled.
Magery has the effects of a Detect, ability to cast spells and a Talent that improves spell casting ability, which is quite a package. We can break that up into Detect Magic, Magic Power, and Magic Talent (see below) which allows mages to vary between their ability to control, empower, or sense magic. Magery 0  is replaced with Detect Magic , which is a little better and it can be improved. Magic Power replaces Magery for Ritual Path Magic, while Magic Talent replaces Magery for the system in GURPS Basic and GURPS Magic. However, either type can increase capability by adding levels in either advantage. The GM can choose to use this for any of the systems in GURPS Thaumatology and even apply it to priests with little effort, simply replace mana with divine, grace, or piety for the Energy Reserve. A 10 point Talent may be to cheap for spells, on the other hand spells could be considered different specialties, or even Techniques (In fact, Ritual Magic, p. B242 already works that way).
Most casters learn how to detect magical energies, in some settings this may even be a prerequisite to manipulating magical energies. While the initial build is very limited it can be enhanced, especially buying off Vague and adding the Reflexive and Precise modifiers.
Statistics: Detect (Magic, Occasional) (Magic, -10%; Vague, - 50%) .
You have the ability to manipulate, and store mana! Each level provides 3 FP that can be used to power your spells. These FP cannot be used for Extra Effort or other purposes and can not be drained by normal means, only powers specifically targeting mana. Each level also grants an increase of 1 for spells and rituals capped by Thaumatology or other core skill (such as in GURPS Ritual Path Magic, p. 5), as a prerequisite for spells requiring multiple levels of Magery, and overpowering spells (where effect is capped by Magery) such as in GURPS Magic. Statistics: Energy Reserve (Mana) 3  + Increased Cap ; 10 points.
You have unusual skill with spell casting and magical theory. This affects Thaumatology and the spells of one system or tradition of magic. Talent with additional magic systems or traditions can be purchased as redundant abilities using the alternative ability pricing (GURPS Powers, p. 11). Instead of a reaction bonus use alternative effects to increase the effect cap on spells that list one based on Magery (such as missile spells). Other Talents such as Natural Caster (GURPS Ritual Path Magic, p. 12), or the ones from Ritual Path Specialists, pp.18-20 in Pyramid #3/66: The Laws of Magic may be used instead. Use the higher of Magic Power or Magic Talent for increasing effect caps, do not stack them.
Powers Based Magic
Sorcery is the signature powers based magic system and uses Sorcerous Empowerment [20 + 10/level] instead of Magery, while Alternative Ritual Path Magic in Pyramid #3/66: The Laws of Magic uses Magery for a core ability. PK suggested on the Steve Jackson Games GURPS forums using Ritual Adept in this manner. Other advantages can be used for a core magic ability with various spells as alternative abilities. However, unless you are going for minor spells they need to be expensive advantages such as Jumper, Morph, Snatcher, Warp, or a leveled advantage. The core or foundation advantage should reflect the nature of the magic, Jumper or Snatcher for summoning things or energy, Morph for body control and shape control abilities, or Warp for movement magic. The potential is only limited by your imagination, for example Trained By a Master for a combat magic system. For a versatile mage Control (Mana), which manipulates magic as a form of energy is thematic.
This is the ability to manipulate the raw energies of magic (mana) itself. Each level can grant a +1 bonus or penalty to casting or resisting the effects of a spell if the target (or targets) are in the area (radius equals level in yards). It can also grant +1 to energy gathering or recovery skills for magic, including the Recover Energy spell where it adds to effective skill level. See Ritual Path Specialists in Pyramid #3/66: The Laws of Magic for another take on this idea.
Additionally, this ability can be used for Power Blocks (GURPS Powers, pp. 168-169) to resist spells cast on anyone in the area. This adds +1 to resist or doubles an appropriate defense, if successful. The rule for only one Block per Turn remains in effect, however each Block can protect everyone in the area.
Common limitations and enhancements can include....
Dance or Song -40%, Aspected 1 College only -40%, see Magery for more ideas.
Natural Phenomena +100% for some gods, typically aspect limited such as fire magic.
Ranged +40% for gods and powerful meta mages.
Reliable +5%/level aids in skill contests of Control vs. Control but not spells.
Persistent +40% lets the effects persist for 10 seconds after concentrating.
Bind Power M/A Default to IQ -3, Max IQ
Used to bind another mages powers using a contest of Will + l per level of Control (Mana) and if successful it pins the power with a +3 on any attempt to break free. Requires a Concentrate maneuver to maintain, unless the Persistent enhancement is added. This will make Magic Power unusable, and possibly other abilities.
Counter Spell M/A Thaumatology - 5 Max Thaumatology
By combining your knowledge of magic with your ability to control the flow of mana you can disrupt spells, either by taking a Wait maneuver for a new spell or a Concentrate for an ongoing spell. This costs 2 FP to counter a spell within range and is resisted by the spell. Range is 10 or Control, whichever is greater.
This is a bolt of magical energy tuned to disrupt the targets stored magical energy reserve. It has no effect on normal fatigue. Statistics: Innate Attack (fat) 1d/level (Magical, -10%) [9/level].
Tools of The Trade
Staves and wands are colorful additions in fantasy fiction, but what do they really do for a GURPS mage? Standard mages can use them as power objects or they could be gadget based Energy Reserves. Purchasing a separate reserve saves points and it recharges separately from personal reserves which results in less down time. Both can be used as weapons (p. B240) and to fire attacks from. As pointing devices wands should increase ACC +1, and do not require separate Innate Attack skills which already work with something in your hand.
Mages combining their abilities is an intriguing staple of fantasy and rules for it are included in various GURPS magic systems and additional supplements such as GURPS Thaumatology and GURPS Thaumatology: Urban Magics. But, how do powers based mages help each other? Sharing energy could be house ruled, but we do have some options for those wanting specific builds. Leech and Neutralize (see below) are obvious options, but very expensive and Affects Others on Energy Reserve is not much better. Dedicated Controls (p. B43), while designed for machines or vehicles can be used to allow other mages to use your energy reserve. Apprentices with Sorcerous Empowerment (GURPS Thaumatology Sorcery) could be required to have this as a known spell and sorcerers or other power's based mages could learn it as an Affliction (p. 00). A version of Raise Cone of Power (GURPS Thaumatology, p. 51-52) or Mass Magic can be done using the rules for Combining Powers (Powers, p. 170-172) to combine Energy Reserves. Once everyone is linked up the leader has an effective Energy Reserve of the highest individual Energy Reserve plus 1/2 the total of everyone else's, though it only has his own energy to start. Each participating mage would determine how much of their own FP to contribute at any given time and each recovers their FP normally.
Want mages to recover energy faster? Consider Breath Control (p. B182), a version of the Psychic Recovery technique from High Psi in Pyramid #3/97: Strange Powers, or Regeneration (ER only) with Accessibility.
You can draw the mana out of another mages Energy Reserve or appropriate things, possibly including powerstones and mana basins. Each of these builds requires touch, though mages involved in ceremonial casting are considered as touching each other. To use these at range requires both Malediction and Ranged modifiers as per Leech (Powers, p. 96).
Absorb Mana: You absorb all the mana from a single target at once, refilling your own reserve or use to power a spell. The energy quickly fades, lasting one second for each point of success. Statistics: Neutralize (Magical, -10%; One Ability, -80%; Power Theft, +200%; Reduced Duration 1/60, -35%; +75% .
Drain Apprentice: Affliction 1 (IQ; Dedicated Controls (ER), +100%; Sorcery, -15%) .
Siphon Mana: Leech (Accelerated Healing, +25%; Accessibility, magical ER only, -40%; Easily Resisted 1, -5%; Malediction 1; +100%; Mana Sensitive, -10%; Only heals FP, -20%; Ranged, +40%; +100%) [50 +8/level].