I will be playing an arcane spellcaster (most likely a PF Arcanist) in my next game and my goal is to make a character that specializes in magically cross-breeding species, creating creatures that are part-something and part-something-else on the fly, summoning cthulu-esque monsters instead of regular outsiders, while also being able to curse enemies with mutations. My ideal endgame goal would be to create a chimeric mount with features of multiple species chosen by me, and to mutate my familiar into whatever I see fit.
As far as storytelling goes GM is sold on that concept, but as far as game mechanics go we have no idea how to even approach this character.
So my question is: what are my options? Are there any feats, prestige classes, spells, skills, anything official that will allow me to do the above?
Key Point: it still has to be a fully-fledged arcane spellcaster. Giving up level 9 spells is a no-go.
If there is no official material from D&D 3.5 or Pathfinder 1, I will be more than happy to accept answers from other editions - it's easy enough to translate and having something is better than nothing.
The only thing that I managed to find is the Alienist Prestige Class, which is utter garbage: basically the only thing it does is change my summons to have the alien template instead of the outsider one, so there are no benefits worth the price of picking this Prestige Class. It has to be something at least worth losing the Arcanist specific feats and giving up the Arcanist level 20 feature.
I’m kinda hoping for something like "crafting" where he could permanently create creatures that will serve and follow him (like it's the case with crafting a golem for example). The Summoner's Eidolon (as an ability) mentioned in an answer below is actually a good idea but the class itself is not.