Looks like much of what you are asking is possible already.
- “moderator” = discourse TL4
- “super moderator” ~= discourse moderator
- category-specific moderation is in the works.
See Description of various user states in Discourse
Also note that discourse has several flavors of user. See https://meta.discourse.org/t/what-do-user-trust-levels-do/4924/6
“Ban super mods” & “Ban admin” should be just a matter of removing admin status and then doing what is necessary about the user account, not really separate tasks in themselves.