So I was thinking on it and here is my idea for how witness votes should work:
If you have:
posted x number of posts/comments total (with an algorithm to check for spammy ones and not count those);
and you've been active (posting x number of posts/comments per month) for the past year,
then you get to witness vote.

The witness vote is weighted just the same for all active members of the community. If a person becomes inactive for a few months, then their witness vote stops counting, which erases the problem of people setting their witness votes, quitting Steem, and still having them affect things. Also, witnesses who quit being witnesses automatically get unvoted as well, solving the problem of people setting their votes and not checking them to make sure the witnesses themselves are still active.

This way, the votes are decided by active, established members of the community, rich or not. And no one has outsized power. The witnesses are still people who know how/can afford the hardware, but if they don't do what's good for the community, they'd lose their spot.