you better find some tailors who work with leather in your area, and ask the question to them, is it possible I think it is, easiest is to make the hem slants toward the waist, so your back would be shorter, and to make the belt not sagging beyond the hem when worn unfastened, you can always add some double tape to secure it in place.
if you go even higher then it requires moving the zipper up, make sure they can do that carefully and not losing the snap on one of the lapel in the process, and of course cut the zip and sew it back neatly if possible using the same holes.
another way to rise up hem without doing anything, is by adding shoulder pad, since it will rise the entire jacket up. if not directly to the jacket then make a vest with padded shoulder and wear it underneath.
if you go even higher then it requires moving the zipper up, make sure they can do that carefully and not losing the snap on one of the lapel in the process, and of course cut the zip and sew it back neatly if possible using the same holes.
another way to rise up hem without doing anything, is by adding shoulder pad, since it will rise the entire jacket up. if not directly to the jacket then make a vest with padded shoulder and wear it underneath.