I know Momiji is very popular, and I do love her character, but I sadly don't see her being in the base roster before any other DOA girl.
It's just... I don't know, I feel like they should have shown her immediately with the other ninjas to convince me.
It just seems like TN still doesn't consider her like a DOA character.
I hope to be wrong, because I like Momiji very much, but until then I expect her to be at least DLC
About Brad Wong, I also noticed he's among the weakest characters in DOA, popularity-wise.
But I guess the same could be said about Leon, Raidou and stuff like that. So I still think he has his fair shot