My god I'd definitely be friends with you if you went Koishi-mode.
Are you sure? It's based off of her dialogue in SA, so koishi mode is really simple. Happy with occasional moments of disappointment, personable/friendly, and (to me) she appears a bit simple minded (well, she is the younger sister). Also, she's polite.
A lot of people in real life inadvertently act a lot like koishi. You may identify them as the friendlier, fun loving (but not in the sex, drinks, and drugs way) people. :|
But if you don't mind people like that, eh, i guess it would work out, but you see, it's a front i use. It's not the real Toast.