That's not near enough people at all. You need enough people so that the population on the forums is large enough so that one group of neckbeards doesn't out talk the rest of the sane people.
Using random numbers, if you invite 100k people a small percent of people won't even get the invite, will miss it, not care, or whatever, let's call it 5%. A huge percentage of people, let's say 50% will only play the game and not participate on the forums at all but will fill out bug reports in game and populate the game enough to internal data can be collected efficiently.
That leaves around 45-40% of the playerbase that know the forums exist. Now, cut that in half for the people who play the beta long enough to actually understand the game or care. Then take 30% of those people as the people who are NOT lurkers.
Mathmathmath
That's like 10% of your tester base actually participating in forum discussion of any substance that you can make serious design decisions on.
Anyway, these design concepts like easy/hard respecs have been done every which way in the industry that I have no idea how the developers are even considering this seriously. I mean, just look at fucking history.