Holy crap! I think I know who the baby Messiah is from that interview and why he's born a mutant.
If Monet is pregnant, and she gives birth to Bishop, then naturally he would be a mutant because his future self is already here in our time and wasn't affected by Wanda's magic. So, in other words, since future Bishop got a pass, baby Bishop gets one too because they're the same person.
In some way that might explain why Sinister is sending the Marauders after chronal anomalies, but for the life of me I can't figure it out exactly.