See, this is why I like smarter people than me. I never thought of raising the number of consensus witnesses. Since that can be increased without limit, then at some point the stake of the minnows can at least elect a witness. Maybe through some combination of increased number of witnesses, per account limits on numbers of witnesses voted for, and making 1 Steem = 1 witness vote, control of the consensus could be prevented to any single stakeholder.
I think it's unlikely, but I'm not a competent mathematician.
Thanks!