I didn't know it was so important that a single spell be able to give any template that the caster wanted. Also, you never said that the effect was supposed to be permanent. With those considerations in mind, I'd say that you're looking some kind of Epic mega-Wish. I mean, plenty of templates add CR to a creature; would you make a spell that can level-up a character? I could see a spell that allowed a creature to trade hit dice/class levels for a template, or 'earn' a template instead of its next X hit dice, but figuring out how the mechanics of it should work, as well as determining how many levels each template is worth (different from its CR boost), is complicated enough that I'll say, have fun doing it yourself.
That being said, I still like my temporary template spells, and I think I'll post a series of them once they're ready.
That being said, I still like my temporary template spells, and I think I'll post a series of them once they're ready.
