I know I commented way back about having some clones of the more iconic basic species (Giraffe, Zebra, etc) but there's some other ideas I've been carrying around - apologies if they're already mentioned by someone else, which likely they may be:
IF Frontier does start to implement birds in the new Exhibits, depending on what, some type of bird or multiples of a bird group. I know this isn't going to happen really, but my dream on that would be a four set of Macaws. If we got the Toucan and Bald Eagle in packs, those would cover my most basic needs. I'm really starting to think even the most iconic birds won't make it to exhibits.
I've mentioned elsewhere, but if they have totally moved on from the standard exhibit system in DLCs, getting a two pack of Cobra or Chameleon would also be an option. I think it's a strong possibility we might get one of the two, but I can dream here, since the work involved in standard exhibit animals is much much less than habitat animals.