Chronotrigger I wouldn't mind a crossover for some of the costumes. As for the whole SE abandoning it thing. IMO Chronotrigger isn't part of a series. Chrono Cross was just it's own standalone abomination of a game that literally felt like everyone came up with their own filler stories and characters then mashed them together and called it a game. Chronotrigger on the other hand is still considered by many to be a gold standard in JRPGs. Because of this SE is most likely walking on eggshells in regards to the title. Cross got it's "remaster" because there wasn't much chance of receiving backlash for changes made to it. In terms of Chronotrigger though I doubt fans would accept any changes to the game aside from a visual update making all the in game sprites look more like Akira Toriyama's artwork and possibly a few new post game dungeons. However anything that remotely changed the existing game story or gameplay would probably hit severely harsh criticism.

Xenogears I think the biggest roadblock is that Xeno line of games has moved away from them as Monolith broke away later having the Xenosaga series of games published under Namco which then later moved to work with Nintendo for the Xenoblade Chronicles series of games after Namco merged with Bandai because they felt they weren't being given the creative freedom they needed to make the games they wanted.