I think that maybe there should be an option for a guild to "buy" the difference in power to complete some of the 150 raids or anything they do not have the manpower to complete.  This should probably be a high cost just so that it's not meaningless to have enough players in your guild to do those raids.  But, I suppose in those guilds that can do those raids this would also help out in a pinch when no one else is available to complete them.

I would think it should just be a guild credit buyable thing.  Or possibly it could be a consumable that can be obtained by players now that I think about it.

Stuff like that, I feel is probably better served with guild skill buffs, and/or player buffs. Strategically casting things to have effect during raid timescale.

Something else we've never considered is actually upgrading/buffing the active raid itself. Maybe as you say, you can spend Credits/Points to boost your stats by a small %, just to give you the edge.

This also ties into your other idea of paying for extra minutes. I kinda like the concept, needs some designs though. I'll have a think