Java Applets? That thing that had exploits like clockwork?
Yeah, that worked great
Regardless did you even bother looking at the documentation of SecurityManager? That would be a disaster to try and support. It can't clamp down per-library, it's all about current thread. Mods run in the same thread, they have to. So now you're suggesting that every. single. call into or out of a mod is guarded manually by updates to a permission manager that you are preventing the mod from modifying via reflection through... magic? Yeah, there's no way in hell that would ever work.
Yeah, that worked great
Regardless did you even bother looking at the documentation of SecurityManager? That would be a disaster to try and support. It can't clamp down per-library, it's all about current thread. Mods run in the same thread, they have to. So now you're suggesting that every. single. call into or out of a mod is guarded manually by updates to a permission manager that you are preventing the mod from modifying via reflection through... magic? Yeah, there's no way in hell that would ever work.