We're talking KOS-MOS again?
Yeah, my opinion hasn't changed much on her. I think she's
possible, but not necessarily
likely. While MonoSoft loves her and she as a character seems to pop up in media and merchandise decently often, Xenosaga as a series seems to be largely forgotten beyond the Xenoblade fandom. As I've said a couple times before, she's like the Morrigan of Bamco; Shows up in a ton of crossovers and hails from a series largely forgotten beyond dedicated communities. Besides, if you're gonna have a Xeno/MonoSoft rep, it'd just be easier to go for the face of the game that got the series noticed and is the most recent (Barring XC:DE, which is a remake and is already represented anyways).
In other words, KOS-MOS is in and her splash screen will be
SUPER SMASH BROS. ULTIMATE X LITERALLY EVERYTHING BUT XENOSAGA