We already know how to solve this problem - it has been solved many times before.
There are good and simple solutions and there are convoluted solutions.
Good solution is to add a fee that scales with the deposit and charge that fee upfront. This will affect everyone in the same way where you will get money on next rebase and not current one. Very simple.
Both large players and small players will pay same proportional price of entry and the cost remains low without affecting current freedom of entry and exit.
This method is easy to implement because we do everything upfront and it solves the problem of constant rotation in and out of the pool with minimal cost.
Other ideas voiced here, go in different direction, questions of manipulation should be discussed in another thread.
Whales do manipulate things, but they also fund this project and have significant voting power, we should not demonize large players in our community because they only appear evil from the outside, it is just that their movements cause an earthquake for smaller players. At some point you may become a "whale" and realize that your normal daily business activities seem very evil to smaller participants - things are never what they appear.
I posted everything I think I can on the subject and repeated my point multiple times, simple fee equal to next rebase of the amount staked is sufficient deterrent and will minimally disrupt current system, it is easy to develop and introduces opportunity to burn some ohm.