Making Master Shadow Gears pretty much you're locking in your shadow gears for this specific job, but when you decide you want to try other jobs as well, you're kinda stuck with a not-so-optimal shadow gear set. Technically you could just reset the enchants of your current shadow gears or sell them and make another set, but that takes too much work and most of the time, noone is really looking for your specific enchant.
I would like to propose to add a reroll system for the enchants of Master Shadow Gears. Something like 2-3 Shadow Essences for the skill slot and 150 Shadowdecons for the stat slot would be nice. Of course, the final verdict on the price of the reroll would be up to the GMs.