It can be done, but to do anything much more involved than shortening the sleeves properly will involve disassembling it down to flat pieces, recutting and reassembing. LOTS of labor time. Easily twice as much time as building a jacket from scratch as it takes longer to carefully pick seams apart so as not to damage anything than it does to sew them.
Actually, even shortening sleeves can be a big time-eater as you need to shorten them from the shoulder, rather than the cuff, if they have zippers or button closures. If the sleeves have knit cuffs (eg: most bomber styles) you can get away with cutting them down at the wrist and re-attaching the cuffs.
To be honest, the labor cost is probably not worth attempting such a project. Back when I was a leather tailor, I'd have started the meter at $200, and warned you that the cost may be more if I needed to replace the lining or cuffs - both of these wear faster than leather and it's silly to do all that work and put in halfway worn-out parts. But that was 10 years ago, so expect to pay more.