Of course I sort of have to point out that neither Russia nor Bulgaria nor Hungary (nor yet the Golden Horde nor Lithuania nor Poland) ever managed to create firm and direct control over modern Romania in the time period
Indeed : I should have been less vague.
I was more thinking about a Galician realm being able to have a comparable influence on Cumanic peoples or valachiesin the Lower Danubian as Hungarian did.
Maybe this kind of influence (rather than direct control) could be more structurated up to evolve up to some form of vassalage as for Transylvania? Granted, Galicia looks (as other late Rus' principalities) quite instable, but with Byzantine support and a lesser focus on Kiev (a rival principality kicks Romanovich out of the Dniepr?)...
Maybe it could counterbalance (rather than replace, tough) Hungarian presence?
so Rus refugee kingdoms in say, Belgorod (on the Dniestr) or Kilia or Birlad would probably prove ephemeral. But that could be just me.
I'd tend to agree, if we're talking about refugees kingdoms, without much deep political structuration to work with.
A more slow process, tough, could proove interesting : at least as Slavic ensembles getting integrated into regional geopolitics (Neo-Sklavinias under Byzantine/Hungarian/Bulgarian/etc. dominance?) may have a bigger survival rate, in your opinion.