You know what? I take this one back. Duros have large heads - just scale the helmets. Perhaps a tricky one to implement but surely not impossible?
1) Okay, I understand the points about the fade-to-black romance. But people are only talking about the actual "sex scene" part. Some players might actually enjoy the romance storyline. And considering the amount of call from the players over same-sex romance, I don't think BioWare wants to just cut it in order to get certain species into the game. Having said that, it's certainly not impossible and a good workaround for when they decide to do it. I just don't see it being a priority.
2) Again, a decent workaround. I also have my helmet off on most of my characters. Still not a priority over compatible species IMO. This is probably the most realistic compromise that BW will make in the forseeable future. Brings in Duros, Iktochi, Devaronian (probably only males though?), Mon Cal, Neimoidian, Nautolan, Cerean... for a start.
3.) Kel Dor could probably just use the echo sound like wearing a helmet. Trandoshans don't sound like humans at all from what I've seen. And can Rodians even speak basic? This may be suitable for those who simply PvP and play endgame, but as a roleplayer I'm not willing to sacrifice... "realism".