As someone who's also familiar with most of the expanded universe:
1. That's not relevant, at all. It's the weakest argument from "authority" I've ever heard. You didn't even make an actual lore-based argument.
2. Virtually all of the EU has been invalidated and is non-canon.
3. BioWare is not going to do this much work just to appease one kid.
4. KotFE's launch is REALLY SOON. Even if they wanted to do this, and every single player wanted this, they can't do it.
5. Joining the Eternal Empire is not "dark" or "evil". The dark Inquisitor, for example, wants power for themselves -- not to be Valkorion's henchman.
6. Personally, I think the Community Cantina events should require attendees to have at least a semblance of proper grammar.