I think this will be a much more consequential change than you're expecting: * The roster expansion is going to dramatically change your WW; * Moving to 8 keepers means 100 of the top players are out of your pool; * Keeping indefinitely under those conditions means an owner's ability to improve their team is permanently constrained.

In my experience, leagues that make changes to add depth to the game use unnecessary complex mechanisms. A simple round penalty works best, and means you're automatically tossing good players back into the draft pool each year (if it's a 1 round penalty, you're unable to apply it to players drafted in the 1st, they go back).

Something a keeper league of mine did in football that you might be able to apply as a compromise here is the concept of a "franchise tag." * You keep X amount of players, but you can designate one as your permanent keeper with no penalty attached (could keep a 1st rounder); * The penalty attaches to the franchise tag itself - can only use once in a 3 year period, so if you fuck it up, it's on you