Nope. Don't see a problem at all considering the level design is bound to be much more expansive this time around. Seeing as how we already fought one in a rather narrow space, they're entirely capable of having one tag along on a mission with us.
I never said there was an outcry for anything. I quoted LinksOcarina who was speaking of the Raloi (that overhyped avian species of cowards). And yes, many people have been wanting to see one since they were merely mentioned during ME3. There's also those out there that have asked for Yahg in the next game, though I wasn't speaking about them or the Yahg.
No, merely mentioning them is not my definition of established. As in a species that has actual history within the MEU. One that actually has a face. Like the Batarians.
Well, you're more optimistic than I am. I can already picture how a yahg would end up blocking the camera every ten seconds when fighting in narrow spaces. I'll pass.
And that's all well and good, but your definition of established is irrelevant compared to the actual definition of established. I don't know, maybe I just take issue with it because the entire point of the yahg's introduction was that they weren't established at all; people had been guessing at the identity of the Shadowbroker for years and Bioware decided it would be fun to subvert all the guesses by making him a member of a speices that no one knew existed - and as far as I can tell from what I've read on development - didn't exist when the concept of the Shadowbroker was first envisioned.
In any event, I'm still opposed to having one on the team. We're already getting a krogan if the leak is to be believed and they fill the niche of big bad ass warrior alien just fine, and they don't take up as much space.