Currently with the way the engine works, you're either in a clan or not in a clan. Only the clan chat channel can have guests.
Whilst technically anything is possible in theory, the time and resource to code this blended system would be excessive as it would require engine work, extensive rewrite of all rank checking scripts (most of them) and then citadels would need to be QA'd from scratch to make sure nothing has been broken in the process. (Bear in mind RuneScript is NOT object oriented, so not particularly modular).
So could it be done? Yes. Would it be done in the next year? Highly unlikely.
Mod Maz
Queen of the Squirrels
RS Training & Developer Lead
20-Feb-2015 09:45:45