I can envision a really wide reaching Pro 12 Competition with a 2nd Div of smaller countries and provinces, it's a decent idea. I can't see promotion and relegation happening in this tournament or in Super Rugby though, even if there is a 2nd Div. It's just not in the culture of the league and the teams will want to protect their commercial interests.
As for Georgia and Romania, the ran Scotland very close in the WC (they lost by 9 and 10 points). Considering Scotland fields 2 teams it's perfectly reasonable to say on player talent alone they could field one each within around 2 years, the only question in financial viability and fanbase size. This is without getting very ambitious and having a 2nd Division.