I really like the multitude of options in regards to different ways to handle magic. However one thing I find that needs a better option is countermeasures. I like the image of fueling wizards, say like this clip so here are a few suggestions.
Prerequisites: Magery, Thaumatology
The skill of applying the knowledge and ability to manipulate magic in a defensive manner to counter hostile spells. It allows a Power Block or Parry (GURPS Powers, pp. 167 – 169). A Block uses the mages magic to reinforce or tailor defenses against an attack while a Parry creates a small magical bolt that disrupts incoming missile attacks.
Spell Block: Roll 3 + (Skill + Magery) / 2 (Drop fractions) with success granting DR 1 or +1 to resist per level of magery or doubling a defensive magical ability such as Improved Magic Resistance or Mind Shield.
Spell Parry: Parry = 3 + (Innate Attack + Magery) / 2. A successful parry subtracts 1d damage from an incoming missile spell for each 1 FP spent. This cost must be declared in advance and is not reduced by high skill (same as a Blocking spell).
Modifiers: Typical modifiers such as Combat Reflexes apply, though footing and shield DB do not. – 1 per hex to subject when Blocking for others or use the Speed/Range penalties for the nearest of the attacker or subject when Parrying for others.
Increasing Effective Range
GURPS Thaumatology offers Adjustable Spells (Thaumatology, p. 39) and Techniques for specialists to offset those penalties, which can include Increased Range. The section Minor System Tweaks includes a section on range adjustments (Thaumatology, p. 35). Below is a variation on Zen Archery for spell casting.
Magical Alignment and General Engagement (M.A.G.E)
By using the Laws of Contagion, Names and Similarity you can reduce range penalties. On a success, add up the penalties for size and speed/range (or Long Distance Modifiers), and then divide them by 3 (round down).
Modifiers: Sympathy section (GURPS Thaumatology, pp. 243 – 246). -10 if used instantly, dropping to -5 after 1 turn of concentration, -4 after 2 turns, -3 after 4 turns, -2 after 8 turns, -1 after 16 turns, and no penalty after 32 turns.