Ok, hope the earlier post made sense: Some sort of language with defined verbs linked to defined effects, defined objects specifying the effects of the spell, and modifiers which can effect the power level or add new effects.

Now, on to the more challenging problem:

Character advancement and managing the cost of casting without having a spell allotment.

First: character advancement. Personally, I would allocate spell words like a sorcerer's known spells currently are (although not so few.) The language needs to be tiered as well (so the verb "Die" can be learned much after the verb "injure") An interesting idea would be a tiered system as well, although I might reserve that for the modifiers only.

An interesting aside: Some wild card words should probably be added into the language, or feats which allow one to cast spells without knowing all the words. This would equate to casting a spell with a chance of failure (and critical failure), similar to the current Use Magic Device rules.

Second: You stated you would like hitpoints somehow effect spells per day. I think that could work- for every spell cast the assigned point value of the spell (point value arrived at based upon the spells used) would inflict a like amount of subdual damage upon you.

The only real problem I see with this is healing spells. A healing spell needs to be able to recover for a character more hit points than it deals- otherwise the character is worse off. Yet if the character ends up with more hit points than when he started to cast, he essentially can cast an unlimited number of spells per day! Even with enforced sleep and rest, this alone makes the character too powerful.

I would suggest using subdual damage, but the mage's body can not heal subdual damage as per normal. If his subdual damage and hit point damage ever combine to be greater than his hit point total, he is unconcious. However, if he is later healed, he does not heal the subdual damage.

Every night, the mage is able to meditate and repair his body, allowing full regeneration of subdual damage as he meditates.

Next: Examples