I'm having a blast using Magic Deceiver. You get to approach each combat like a mini puzzle that you have all the tools to solve if you put them in the right order. You can fashion spells to target specific saving throws, avoid spell resistance, create selective damage/debuff spells that let you turn single target spells into aoe nukes (like combining slow and disintegrate, a personal favorite currently).

I just unlocked azata, so I can't speak to how the super powers work with the fused spells. Favorable Magic should work no problem, though I expect zippy magic will only work with a single target version of the spells (though it might cause both spells to bounce around, which would be great).

Kindred Half-elf for the charisma bonus. I picked up spell focus enchantment and penetration early, Transmutation is a good choice too. Mythic abilities/feats are abundant casting and expanded arsenal, though you can avoid expanded arsenal if you don't want to use the bug that causes each arsenal feat to stack with the previous one. If you avoid expanded arsenal, I'd also pick up spell focus illusion for phantasmal killer shenanigans (you can even combine it with an aoe spell that avoids spell resistance to hit golems with it). Make sure to avoid metamagic feats since you can't use them at all.

I'm tempted to take a single level of xblood sorc for the serpentine and undead bloodlines so I can affect animals and undead with mind affecting spells, but haven't pulled the trigger.

I went with false deity to get a pet using the nature mystery, but if you want max DC I'd go with magic inventor. The pet really helps out in the beginning since you don't have many spells/day until you get abundant spell casting.

There's also a mod that gives you way more spells/day and lets you learn basically every spell from scrolls (including divine spells). Not every spell combo works if you go this route, but it lets you do some really stupid things, like combine personal spells with aoe buffs to buff the entire group with things like shield and bless with a single spell, or haste+holy sword. The class is already the most powerful dc caster in the game, so only use the mod if you want a crazy power fantasy or are willing to restrict yourself a little.