Many small groups go into abyssea to farm +1 seals and +2 items with someone subbing BRD in order to proc Grellow. Since currently all instruments are equipable by BRD main only this reduces their efficiency.
How about adding both wind and string intruments that could be equipable by other/all jobs.
If need be, could start off with all mage jobs then just add some for ALL later on if the need is there.