I'm just starting my Fire GAxe trials. Everyone knows the challenge in doing fire magians - fire weather is woefully under represented in Vanadiel. So, for the most part, those doing fire trials are stuck with the slowwww grind of 1 point per kill on firesday.
What would help would be to change level sync so that you could synch down even when solo (set your level to any level less than your current level). This would open up the options for magians to other regions where the mob level is too low for those that don't have someone of the right job level to sync to.
Rather than add an option to Party Sync, it would probably be easier to do this in the job selection menu, only when in your mog house. You could set your main job level to any value less than your max. It would then be possible for a party to sync down to that person's level.