for the qualifiers, at least that's what the rules were last season, you could join any of the 3 qualifier no matter if you had 0 russians or turks, I think there was a Turkish team in the EU qualifier this time around as well - Digital Athletics
and about xeta, this specific ruleset only applies to emea, but if something like that came to fruition in na or korea, i think they'd follow the lol example, where players stop counting as imports after playing and residing in the region for 3 years, so xeta would not count as a local player in NA just yet.
say that 3 years would already have passed and he was considered a na local player, and he decided to move back to korea, I think he'd be immediately considered as a local player in korea