Would that same thought process not apply to rebel vs. Imperial, though?
I haven't read enough of the New Jedi Order stuff to know if I would personally have an interest in the Yuuzhan Vong or not, but if there's a demand for them, they should get made.
I don't really get the mentality of "I don't like it, so it should never get made." You could always just not buy it.
I think the issue here is the the whole EU of the Vong invasion was how they were a technologically advanced force that decimated the galaxy - which to bring into a game that has any hopes of balance between forces would just end up screwing it all up. Bit like trying to have a Star Trek themed version of Armada and then saying "Oh, lets add a Borg faction - that would be equal to the others".
As others have pointed out elsewhere on this board, by all rights, the Imperial Navy should outnumber and outgun the rebels at every turn. But they don't, because the game is based on a system of both sides bringing an equal point value worth of ships to the fight.
Why would that be any different for including another faction?
Because it gets considerably less "fun" if you are only bringing a single small ship that is worth the points of your entire enemies fleet - either that or you have to completely nerf the stats, and then they arent the Vong that players expect, which begs the question why bother then?.