That'd be pretty cool. Yet there is no guarantee of a bad actor buying in and then blowing up the idea.
I am fine with the concept, but if we can think of a compelling reason for someone to want to be a whale at that point or above that cap then that would be a good reason.
For the good of steem/it/busy, etc. is one thing?
Yet often they still want money. It could be argued their stake is gaining value, but if they are not voting then they likely are not earning anything liquid, and they cannot actually spend their money without powering down.
As to convincing them... I've monitored some of their activities for months and seen various investigations. Some of them are clearly in it for the money and don't give a big damn about the community as much as being able to use their power how they see fit.
Capping the power will likely not fix the problem in the long run. It leaves itself open to gaming, and in a sense if they do game the system which I fully expect some of them would (because, they do now, and they've been talked to about it and indicated they don't give a damn what anyone else thinks), then it actually could be worse. Right now we can identify them as one account.
Once they have their power disseminated across 50 accounts controlled by a simple program (not difficult to make) then it could be trickier to identify who they actually are. They could then even shell game it.
I see this as looking at the problem with short term vision, and ignoring the long term ramifications.
If we can think of it , we need a compelling reason for them to want an amount of power beyond the cap. If they cannot vote, then they cannot earn curation rewards, which is their liquid income, and there is no benefit.
This is reality. Not everyone gives a damn about the GOOD of the community, or other people. Some of them may speak of the good of the community when it is positive PR for them, but watch their actions and there are some that don't seem to actually care much about that.