I think we might see something in the future about Elena and Layla if you're on Elena route. I don't know if anything changed before rework regarding Elena but before player had to have good relations with Layla in order to get closer to Elena, so there's def potential there and all the drama.
Gabi, like you said it's an affair destined to fall. I mean nothing serious can happen betwin the two. That kind of relationship doesn't last. Both of them constantly need to hide and it's guaranty that someone will figure out what's going on betwin the two. And again drama.
Nikki/Cara are both good. The only down side would be if Andres married their mom however since Andres is out of the picture they can continue with their relationship.