Yes, I'd go with leatherworking, as long as one of your alts is doing the mining to feed your engineering and skinning to feed your LW.
With LW you'll be able to craft your own armor. Once you hit outlands and start getting rep with Kurenai, you'll be able to make an awesome Netherfury set. And of course, heaven only knows what else with the upcoming patch.
High level crafted items also sell VERY well on my server, so it's a win/win situation. Just make sure to take the Dragonscale Leatherworking path so you can make mail items for yourself!