Diamondinmyeye
Regarding your poll, I would just like to say that I don't think using recipes or recipe items as a way to level your buddy is a very wise idea as those items can be purchased on the marketplace. Not really sure if that's what you're entirely getting at, but I would definitely be opposed to that aspect.
I would love to be able to have buddy modifiers, similar to Pokemon evolution stones. Get a recipe that creates the modifier, craft it and then use it on your buddy to give (only) its appearance a change. This could change their colour, give something like a plain fluff a theme, add items like armor or a sombrero to your buddy, etc.
It would limit possibilities, but still add the element of customization that gaians love.
Recipe items would affect the way it evolves, not actually evolve it.
Say, you feed an OMG 100 pumpkin fluff cottons, in this case it will turn into a black & orange OMG. If it evolves after being fed the evolution items, it will be a black and orange OMFG.
Lets call them "special" evolutions for those willing to pay up the recipe items. A sort of "GOTTA COLLECT THEM ALL" feat.
Bonus material for when you have a shitton of recipe items and don't want to make recipe's. Maybe even a certain random combination of recipe items would make neato-looking versions, eh?