Pseudokit possibiities

[Miloch]

I want to make a sort of "pseudokit" for a multi-class character (cleric/mage). I don't want it to be a real kit, largely because he's already kitted as a specialist mage.

 

So basically I want to simulate him being a priest of a specific god, having access to certain spheres and not others (a la 2nd edition, Divine Remix etc.). I also have a few custom spells I want to give him at certain levels. Can I just remove verboten spells from his spellbook and add the others, or is there anything else I need to look out for? Will this get hosed on level-ups or otherwise?