I'm sorta baiting for someone to prove me wrong. I'd never heard of the plane till someone mentionned it in a thread much like this one. Gonna go read up on it. Personaly though, I think the Finns deserve the Brewster way more than the tiny number of french players do the D520.. As far as I can tell anyway.
Well, when it comes to French planes, M.S.406 had more impact, more were build (1000+ vs 900+), and it has seen more combat as well (used by Finns also).
Either way, Brewster, MS406 and D520 should all be low priority. They'd be ok for few selected scenarios, but otherwise, typical hangar queens.
There are huge gaps in Russian, German (bombers) and Japanese sets which should be filled first (IMHO).