Hi,
It would be possible to make a command like /switch to change ranks, and it would work, HOWEVER;
The current system we use for ranks requires the person to be kicked for the title to change successfully, so whenever you wanted to change your title you would get kicked, the problem with this is that it is an inconvenience to players, and it could potentially cause spam with the kick message - "Your rank has been updated!". Another drawback of this is that our system will give you certain permissions for your rank, so if you were a VIP and a Veteran you might not be able to use all the features you've paid for with VIP if you chose to use the Veteran title.
Regarding the mob arena class - Armour and weapons repairs itself (as mentioned above) , so there isn't much use for the rank, thanks for the suggestion though!
Hope this helps!
-WW