bettas can be community fish, but you have to be careful and research what you add them with.
I've heard betta's aren't good friends for angels, and swords are aggressive towards bettas, gouramis are also meant to be a no-no as they are both antabanoids and therefore both bettas and gourami are highly territorial.
Guppies are often victims to bettas, as bettas can mistake them for other bettas and attack them.
So I think it's very unlikely a betta would be good for this tank, sorry!