The main goal has always been to avoid one single entity throwing out all top 30 witnesses ...

Why not just reduce the number of witnesses one single account can vote for?
Five to (at maximum) ten witness votes per account would be enough!
At least it would make it somewhat harder for one entity to control the whole blockchain. I know it would still be possible to use multiple accounts for witness voting, but in that case the stake had to be spread on different account which resulted in less voting power.

Already now the influence of - for example - @freedom on witness voting is far too big.