Would it be possible to add player keep inv command so i could add per player keep inventory similar to whats available with essentialsx and luck perms.

I believe there are fabric mods that do this already. Give this search a try! https://fibermc.com/?search=keep

Let me know if that gets you what you need!

Closing due to inactivity, and I believe other mods provide this.

Problem is there is not options that fit this any all those mods have not been updated since 1.19.4.