Just idly wondering here.
What if the standard GURPS Magic system was tweaked so:
- there was no penalty for cumulative spells "on."
- but no spell could ever be maintained completely for free.
So you could have, say, 10 spells on with no penalty, but a Cost 2 to cast, 1 to maintains spell at skill 15 would be 1 to cast, 1 to maintain?
I'd expect you'd see skills stay close to their default levels a bit more often, and most of the saved costs put towards FP, Energy Reserve, and so on. Socially, you'd probably find Enchantments even more prized and Power Items/Power Stones even more critical.
In combat, you'd get a lot more buff spells cast and attack spells used, since "spells up" wouldn't reduce the cost. But you'd also have less spells kept up, because they'd run down your energy eventually.
Actually, you could probably get away with saying any spell reduce to 0 cost instead had the cost halved to 1 FP per 2 durations maintained. You could extend that to higher levels, so skill 20 would put a 1 to maintain spell down to 1 to maintain every 4 durations. Basically, pay your 1 and get up to 4x the duration. A 1 minute spell with cost 1 to maintain would be 4 minutes (or any fraction thereof) for 1 FP. Or just track fractional FP, I suppose, and say anything reduced to 0 is 0.5, reduced to -1 is 0.25, anything reduced to -2 is 0.125, etc. to maintain. Probably not worth the headache.
Just a random thought here - it would radically change magic as a power, with only a fairly simple change to the rules themselves.