[...]otherwise, it could possibly end up imba
I think you miss the point. FO beta tester will only play the game and won't be able to change settings directly. I am quite sure the FO staff will play their game theirself, but want to hear some more opinions.
Being nervous the game could get imbalanced just because beta testers will be recruited from donators is definitly not logical. There is no proof or disproof the donators won't be capable enough testing the game.
At the beginning of this thread I hoped and believed that there won't be no flaming, whining or arguing at all. The beta key is something like a reward for me, something the donators get because their financial support show high interest in the game. In fact, there is no real flaming or whining, yet. But I am curious about the next 20 posts.

Now, the arguing begins. "Ooooh, I am so damn nervous, maybe the game will suck. This would be awful, because...aeehhh....hmmm...to be honest - I haven't paid for the game. I didn't even have to go to the game store to get the game. I just downloaded it. Fast and easy. Hmmm.
Nevertheless - I do have significant arguments why not only donators should get a beta key."
Oh man, these guys are developing this game for years. The balancing in V3 wasn't perfect. Neither was it a disaster.
Did you trust the staff so far? Trust them now! I do.
The staff's decision is absolutly fair.
Oh, and there will be support für V3, as they mentioned. Problems will be solved with a patch, for sure.