I found a way for a non-host-ranked super administrator(one admin level below host) to ban other admins, in very specific circumstances. Untested, but it likely works.
Basically, un-unban takes one argument, the name of the banee, and advanced proccall can only work with single arguments.
Actually, the rest of the admin process is quite secure. Clients don't show up in the edit variable menus or the proccalls, and the admin panel object for each admin is likewise hidden. Otherwise it might have been possible to use the built-in kick feature of the admin panel that only applies when an admin tries something they can't do, like kick/ban another admin.
My reccomendation would be to revamp the admin power levels system to have a proc return a numeric value(between 1 and 10000, the extra digits for future expansion. Normally returns a multiple of 1000 or so) given the admin level(special case: -1 == instant ban on proc entry, 0 == regular player), and compare that.
Additionally, admins below the host level should be able to remove admins of a sufficiently lower level(at least 2000 admin levels below them?), and host-level admins should be able to add lower-level admins mid-game.
Admin procs should be given based on admin level, rather than relist them all based on admin title, as some super administrtor verbs AREN'T available to hosts, even though hosts have a higher level.
I could do all that myself, but the code merge afterward would be annoying without either a Johbson or a source control server to merge code automatically and share it instantly.