dave2008
Legend
Excellent point, thank you, Quickleaf. That's the kind of impact I was asking about, and I hadn't thought of this. It's still a rough sketch of an idea.
Definitely a factor to be considered.
I am not sure how your are tracking base hit points we do something similar (bloodied hit points) that we track separately. Thus spells that use HP works as normal. If you you don't track it separately you could just add the characters base to the spell HP range or generically add 10 (or whatever you deem appropriate) to the spells HP range.