Basci HTTP Auth with with the salted SHA512 algorithm rather than MD5???

That could be problematic as you need the salt and hash to verify the correct password. Storing it in table space is an option, but that isn't a permanent filestore and you risk forcing password resets for everyone. If you wanted to go down that route, you'd need to generate a CSPRNG for the salt (for SHA512 it should be at least 64 bytes) and prepend that to your password before hashing with the built-in SHA512 iRules command. rand is not cryptographically secure, but perhaps now with proc support, someone wants to take on building a CSPRNG proc for iRules?