I'm concerned (not objecting) about the 50% rule being dropped, but perhaps not for the reason people would expect.
The board are going to be empowered to do anything they like. The community are going to be asked to put their trust in these people.
Suppose someone gets onto the board with less than the majority of the communty approving of them.
Now suppose something goes wrong for an unavoidable reason.
The natural reaction of people is to look for someone/something to blame. In an online community where it is possible to hide behind the screen the worst in people comes out and things get said that perhaps would not be said in a face to face situation. Any candidate with less than a 50% approval will almost certainly become a pivot point for the community. Issue like "why was the board elected without a majority of community membmers supporting the members?". The community will split at a time when it most needs to pull together.
Now if the majority of people here think I'm being over careful I'll drop it. My intention is to raise this concern, if you decide to drop the 50% rule and something like the above scenario pans out at least you can watch for the early signs of that split.
I understand your concerns, but what's the alternative? If we don't get at least 3 people with 50+% what do we do? Holding another election isn't likely to help, it will just get the same result. If we get 3 people with 50+% but not 5, then it's not really a problem since the 3 that have wide support will have a controlling majority anyway (assuming everyone turns up to meetings, at least). Remember, we're not really trusting this board with much since we don't have anything to trust them with yet. The worst they can do is waste a few months. (At some point, they'll be receiving membership fees, but if they get that far then they've probably earned everyone's trust.)