Not sure if this was suggested already, but it's really annoying that you can just get rid of wither sickness by dying. I feel like with a config toggle, you should keep wither sickness when you die so you have to cure yourself normally to get rid of it.
I play on a server with my friends, and they die a lot, so I have to use /effect to infect them again with wither sickness. It would be more challenging and you wouldn't be able to just cheese it.

Will be implemented in the next 1.18./1.19 release