Nothing crazy, but enough to add to burn and prevent reward dumping. Nothing changes for hodlers and is relatively short time lock, so shouldn't be a big deal, even for big investors. People would also still have the option to compound rewards right away.
Everytime someone harvest cake, offer them 4 options for collecting rewards.
All penalty fees end up getting burned and therefore helping reduce supply.
If everyone is cool with and supposedly hodling anyways, then this shouldnt be an issue. 3 weeks is shot amount of time.