Shame we don't have an ant farm or bee hive exhibit since they are an interesting example of individuals not really showing signs of intelligence but the whole superstructure of the organism becoming almost like a conscious mind. Maybe you could use the termite mound enrichment and display that?
I wish for Bees for such a long Time already

Is there a Zoo that exhibits them in a big Formicarium that has a Opening that leads out of the Building so they can collect Nectar? (At least that's how I would do it)
A Formicarium would be cool. Even though they are one of the most interesting Ants, Leafcutter Ants probably wouldn't be the best Choice for the Game if they should decide to make them realistic. One Colony of them can get so big that it can fill a whole Room. I think the best Choice for Ants in the Game would be selecting a Species based on Size to guarantee maximal Visibility.
I've used the Termite Mound once just to exhibit the Animals (was in a Indoor Elephant Enclosure though, so no Close Up View for the Guests) and even made a Education Sign for it. Would be so nice if we would have a Version of it with a Glass Panel on one Side, so it's possible to look inside. I guess this could probably be done by expanding the Termite Mound by the Use of Fake Tree Pieces or Rocks and then placing a Billboard there but from my Experience with Billboards it would look washed out and they would probably always look way too oversized