The negative of PoS is (in my opinion) the freeze of the yours ETH for validate a block, but maybe staking pool could resolve this problem?
IMO this already implemented to make sure the stakers will not unstake and stake their token again anytime because this can affect the stability of the network once ethereum will go all in the POS system.
I guess anyone knows this if some address got slashed caused by their performance are so bad. The locked period being created to keep the network validators became stable and it will also make the stakers have a commitment to the network