While his personality comes and goes, Warren, at his best, can be pretty laid-back and charming and come across as a 'safe' mutant, both visibly so (because of the wings, not 'scary' like Nightcrawler, or 'hiding as a normal person' like Alex). That makes him a decent choice for easing into mutant/human PR relations.
As opposed to Monet, who is... less diplomatic by nature, and also a bit of a 'stealth' mutant, in that fearful folk can point to her and say, 'she looks just like us, they could be anyone!' I like Monet a lot, but her and Emma and other more attitudinous mutants (like Magneto or even Xavier, who can come off as patronizing and elitist) might not be doing the species any favors with their hauter and superior attitudes.
Put your best foot forward, as they say, and mutants like Warren seem more like a 'best foot' for diplomacy.
Jay Guthrie, from more of a blue-collar aw shucks cornfed background (and a similar visible-but-not-scary-looking appearance) would work even better as a mutant spokefolk, if he didn't, yanno *hate being a mutant.*
Other visible-but-not-scary mutants like Bling! or Mercury could also serve well there.