Two weeks ago, I posted about Modular Powers, which is a system for flexible magic/powers that I worked out for GURPS. Since then, I’ve received a good amount of feedback, and I think I can just go ahead and simplify the system even further while giving it a more appropriate name.
Wildcard Power Pool is 2 points/level. This must be taken in conjunction with a base ability, and the level of the Wildcard Power Pool cannot exceed the point cost of the base ability. The base ability can be a raw advantage or it can be a modified power, but, if the base ability has a Power Modifier, the Wildcard Power Pool abilities must have the same Power Modifier. To use the Wildcard Power Pool, choose any other ability whose cost, after all enhancements and limitations, is not greater than the level of the Wildcard Power Pool. Only one of the base ability or the Wildcard Power Pool ability can be used at a time, and switching between the base ability and the Wildcard Power Pool ability or between Wildcard Power Pool abilities can be done at the start of one’s turn as a free action. To use multiple abilities at once, one can buy multiple Wildcard Power Pools.
Wildcard Power Pool can only be modified by the Limited Scope limitation (and I prefer the version from Ritual Path Specialists from Pyramid #3/66: The Laws of Magic as a basis)—e.g., Limited Scope, Abilities related to Druidic magic, -20%; Limited Scope, Abilities that create or control fire, -50%.
Furthermore, the base ability may be changed as part of advancement. As long as the level of Wildcard Power Pool is equal to the cost of the base ability, the points in the base ability may be spent to purchase a more expensive base ability. Optionally, if the level of the Wildcard Power Pool is less than the cost of the base ability, the difference between the cost and the level is the temporary cost of the previous base ability until the level of the Wildcard Power Pool is equal to the cost of the previous base ability. For example, if Zambazor has Flight  and Wildcard Power Pool 30 , but he wants to upgrade to a more expensive base ability, he must also pay 10 points (the difference between the 40 points in Flight and the 30 levels of Wildcard Power Pool) to keep Flight as part of his pool of available abilities. If Zambazor takes a higher level of Wildcard Power Pool, the original cost of Flight should be lowered in the same way.
Obviously, I started with Modular Powers. I turned the base Modular Abilities into Modular Abilities (Slotted Cosmic Powers; Physical, +100%; Reduced Time, +20%; and Trait-Limited, Alternative Abilities, -20%) for 14 points for the base cost, + 10 points/level. It’s important to keep Reduced Time for instant configuration because you already have to spend a moment switching between powers anyway. It also makes the cost a bit smoother, which is nice. If you have Flight  and you can take Alternative Abilities up to 8 points, then you need Modular Powers 8 —remember that 14 points of that is from the base cost, so the remainder is 80 points.
If you turn Wildcard Powers from GURPS Supers into a Wildcard Power Pool that costs 2 points/level, it comes out to about the same price without the base cost. If you have Flight , you need Wildcard Power Pool 40 .
At that point, I can just say that the Wildcard Power Pool requires an Unusual Background (that I would personally make equal to an extra level of power Talent for the character) to make it cost the same as Modular Abilities. Or, of course, I could just drop the extra cost. If you want to require the Unusual Background, go ahead!
This works better. Instead of using a simple ability to justify a complicated one, it seems much easier to use a complicated ability to justify a simple one. There’s no need for base costs or extra modifiers or even a new power Talent, but the math is all the same!