Well first off Zetsu's moves are usually weakly wood based if they get their hands on some senju DNA.(otherwise they didn't fight)
The Second thing I wanted to put out there is that when Zetsu fuses with an Obito it should grant the Obito some for the Zetsu base stats like Obito did the first time he fused with zetsu but the boost would not be permanent, just until they split up again.
When fused the Zetsu should be able talk and the person fused with them should be able to hear them.
Zetsu should be able to really fuse with just about anyone who allows them to.
So When Black Zetsu takes control of a body it only lasts awhile, there should be a meter somewhere to tell someoen how much time they have controlling a body.
Since Black Zetsu could take control of bodies i'm sure he'd be able to take control of a corpse and use it's techniques so maybe that could be a thing for black zetsu.
Another thing that would be nice if Zetsu clan had is if they could split up and instead of just changing their body maybe they could pick which zetsu to become and send the other half elsewhere or something.
Last thing, Zetsu uses a type of clones that allow him to listen in on people's conversation or stick to others and suck or give them chakra.