You'd get along with my co-mod on The Borgias.
She also doesn't like non-Russian actors playing Russians.
As for Caitriona and Saoirse(damn, those Irish names are tough), you'd be correct that they were nowhere near old enough at the time. I think Caitriona was still a Victoria's Secret runway model, and Saoirse was playing Michelle Pfeiffer's daughter in a movie.
Speaking of, Saoirse has played Americans before, you know.
I agree, you don't need big name actors, but you know Hollywood.
And I can't wait for New Mutants to come out so we can have actual discussions about it.