The only reason the QF Regional Pilots are not covered by AIPA is that they, as a group, have not approached AIPA for representation.
AIPA cannot approach them under section 118 law as it would be deemed poaching and significantly bolster the coffers of the AFAP under legal challenge.
If the Regional Pilots as a group decide they want a career path into mainline and are prepared to sort out their seniority issues as a cohesive group, then I am sure AIPA would be delighted to take them on board.
It's the only way forward and must happen IMHO.