Wankery... Good word, that. 

Honestly, I doubt there's any firm and solid answer to this hypothetical question without turning it into an actual experiment and IC with other players. I can only say that for myself, I think people can be capable of playing a separate species they didn't come up with. After all, there are plenty of rpers who write as wolves, or warrior cats, or horses, or dragons. 

Whether or not they'd be able to rp the mindset of these aliens to your satisfaction would be a secondary, but also important, question. If, in making this alien race you want to allow the rpers to play around a bit and help them grow, they've got a slightly easier time of pleasing you, but there's also a chance things won't go in the direction you might have thought they would. If you start with a very firm grasp of the mind and mannerisms and methods of communication and social structures, etc. that's great for you, and there might be some willing to still give it a try, but they're far more likely to disappoint simply by missing the crucial details that can't necessarily be set into written words without oodles of explanation. There's a good chance they'd be just as frustrated trying to figure it out as you might be in having to read them not managing it quite the way you envisionned. (I keep saying you, it's a hypothetical you, yep)

Multiple people could agree to play a certain mindset, though I'm sure they'd all like the chance to individualise it at least a little, unless they're playing the same overall mind in different bodies and it's basically the same character. That might get iffy... Or crazy fun, I dunno. 

Eusocial is probably the easiest to understand and the simplest to explain. It's a group structure, so it would also make it easy to have plenty of characters in one spot and plenty of NPC examples for them to follow. People know about ants and wasps and molerats, and about their caste system, and it's not hard to look up if they want to. 

I don't think it's necessary to make aliens like humans to be playable, they just have to be understandable for humans. This does limit the options alittle, but there's still a huge range of variables that can make a mindset alien to most humans' way of thinking without making it impossible for a human to understand the thought process that reaches that point.