Are there any workable proposals on the table that can address this?
There are many solutions who have been discussed at lenght in the past couple weeks.
I proposed the user/moderator thing, dan atstarlite proposed to create 2 type of steem power ( steem stake and steem power), smooth proposed a system where users who vote would be penalized by receiving less inflation and I've seen others like you proposed modified version of my proposal . Those are all workable, the million dollar question is do people care enough to want any of them?
Another thing that could be done is to remove curation reward so that whales have more incentives to delegate their voting power. I think many won't even bother voting if there was no curation reward, this and removing the curve will probably improve power concentration. Whales understand that if they give up their power the retention will be much better but most are too greedy so if we remove curation many will probably refrain from voting.