From what i looked at its pretty clear imo that vote selling for your hypothetical whale is still a more lucrative deal then curation after vote selling markets adjust to increase in curation. And they will.
After the passive investors move away from bots and into vote selling you will have a huge supply of votes on MB and SS.
Once the balance is struck, you just made it much cheaper in liquid STEEM/SBD for the vote buyers to get on top of trending. The vote value you had to pay 400 SBD to get on top of trending, now you will be paying around 250SBD for.

50/50 changes absolutely nothing and potentially makes it even worse. These calculations you made seem to be right, but they are just one side of the coin. No one seems to even want to look what side effects this change will have.

If vote selling is still the profit maximizing option then there is absolutely no way that passive bot investors or semi active whales, after they realize it, wont move to vote selling...
If they are doing "nothing" now and this change happens, they will continue to look to do nothing and earn as much as they can.
Vote selling and getting "smaller amounts of liquid assets and more curation" is still superior to "just curation".

This proposal slightly cuts the passive income of bot delegators (now vote sellers) since more liquid gains is better then more SP gains, but remaining passive is still the most lucrative deal.
Also, now you did a great service to current vote buyers.

You didnt change the content placement problem, you made it worse since "going trending" is cheaper now, smaller account behavior wont change much since they earn almost nothing from curation, and you moved the earnings from the non-boting creators to whale curators.
Is this a smart thing to do when retention is a big deal in a bear market?

Im going to ping @blocktrades since he upvoted me a few times to see if any of what i wrote makes sense to him.