Have you considered working out a system similar to the Psion Handbook's one?
It does sound like what you've got worked out, so you're on the right track in my opinion. This way a character has a certain amount of 'points' dependent on level, artefacts carried, and high scores. Some dreams will be cheap (hence castable often) and others (like the Dispersal or Dream of Unlife) would cost a lot.
Maybe even have the really powerful ones (like Unlife) have an attached XP expenditure to cast them? Kind of like creating a magic item.
Just a few suggestions. It's late.
I could make a very basic Frontpage website if you wanted, and then tinker with it. I've got a lot of html savvy mates, so I'm sure I could con/goad/bribe/beat one of them into aiding.
LR
