There doesn't seem to be a lot of ROMs for this phone yet. Or is everyone using ROMs from the HTC EVO 3D?
Just install Go SMS or Handecent. That shouldn't hold you back from flashing a ROM.
Apps are not the reason MMS doesn't work.
Baseband information is. Virgin runs on different baseband settings than Sprint phones do despite being a Sprint owned company.
What ROM are you using?