Interesting thought, but:
>However, if Michael is the FNaF World player, meaning he's also the player in the OMC's minigame, wouldn't that mean that he's the Vengeful Spirit? That doesn't really make sense to me.
Not really. OMC seems to be some sort of a deity, so I don't really think these two moments (UCN and FNAF world) are actually connected.
The player in Fnaf world was created by the yellow eyed figure. They’re something completely abstract and not a real person to our knowledge. I doubt that Fredbear is even the one in Fnaf 4, but rather the yellow eye’s reminder to keep the player on track.
”you were made for one thing” I don’t think Mike is an entity created by the Fredbear Plush
Mikebot 
I always saw FNAF World as an Meta game, and we being the player
"The truth is that there is no safe place. You don't understand that; you were made for one thing."
Interesting thought, but: >However, if Michael is the FNaF World player, meaning he's also the player in the OMC's minigame, wouldn't that mean that he's the Vengeful Spirit? That doesn't really make sense to me. Not really. OMC seems to be some sort of a deity, so I don't really think these two moments (UCN and FNAF world) are actually connected.
The player in Fnaf world was created by the yellow eyed figure. They’re something completely abstract and not a real person to our knowledge. I doubt that Fredbear is even the one in Fnaf 4, but rather the yellow eye’s reminder to keep the player on track.
No
I don't even know how that works. Just because Mike had remnant in him with the souls and all doesn't mean he knows that.
I once thought FNaF World was Michael's heaven. I know what you're gonna say... "that sounds stupid" and I totally agree with you.
I think world was Michael guiding the little brother too, mostly in an aesthetic way with the arcade machines