Re: could they do a show with "realistic" aliens?
As for communication, the UT makes it possible for aliens in Trek to talk to one another, so if they did have a language it could be interpreted. If they didn't then the cast would need to include either a telepath (to communicate mentally with them) or a specialist in non-verbal communication (which would most likely be a counsellor, diplomatic officer or cultural specialist).
Avatar: Captain Susanna Leijten, U.S.S. Silverfin NCC-4470, Border Service Third Cutter Squadron
Manip by: FltCpt. Bossco (STPMA)