Basically instead of spawning as a regular player, we would spawn as this.
Us, the player would have more player qualities than villager qualities.
The Mob, (we would be able to breed with villagers now, lol) would have more villager qualities than players.
Us, Half-Player Half-Villager:
Now i'm not totally sure about this, would we spawn in with randomized items? Or would we be able to get items more easily? Would we choose what profession we have and changed later on in the game, or spawn with a randomized one? (this would affect the items we would spawn in)
Can we get infected? If so, that would mean zombies would not attack us, we would get more health, be slower (?) and maybe even make our zombie friends tougher (giving them armor, weapons etc)
The Mob, Half-Villager Half-Player:
I'm also not sure about this, but would he gather resources and trade with his villager friends for free? Or we would give him money (emeralds) to be able for him to trade with the villagers and get more stuff? Would he defend himself or give his friends (the villagers) armor so they're harder to kill?
As for the infection part, i really don't know.
Sorry if i'm so clueless but this idea was really hard to finish