I just wanted to throw in a suggestion I got from Dragonstar. Adding ECL after creation is something the system wasn't designed to handle. No matter how you do it, progression is significantly screwed up, and besides that, you "earned" whatever you got.
In Dragonstar, there are magic items that can add a template to your character, notably the Celestial Conversion divine spellware for Paladins. If you get one of these, you immediately gain the half-celestial template, without wings. It's priced at 250,000 credits, which is expensive, and pretty much equivalent to 250,000 gp. As a rough rule, you could say that (ECL)^2*25,000 gp is the value of a template, and then apply that to the character's wealth per level.
It still means that a level 4 werebear is probably too powerful for the party, but at least you could quantify it without neutering the character's progress for 6 levels.