There are a large number of users who have elected to use third party tools to simplify gear swapping. This is more something to assist those who are still limited by sticking to the in-game system. This idea may have more specific benefits, but it comes to mind specifically for mages--particularly to the elemental obis.
If you aren't using the third party tools, you have to create additional macros to swap in the appropriate Obi, or try to time the gear swap midcast manually. If we had the option to lock the waist slot, we could equip the appropriate Obi when the conditions are present, then just use our normal "Nuke" macro to swap all the other gear pieces as usual.
Just a thought, it may/may not have any merit for other situations--but it could prove beneficial to mages at least.