Personally, I'd be more comfortable with allowing Ballistics to add to weapon skill when calculating how many actions a character can spend aiming (after a certain range; perhaps past 100m). So, if you have Rifles 6 and Ballistics 6, instead of 3 actions, you could aim for 6. It's rough, but I think it has potential.
Anyway, personally, short arms and long arms as the only two firearm skills makes a lot more sense to me in relation to the rest of the canon skills. Spell casting, after all, only has 2, and they're plenty powerful. Mundanes could use an extra bit of help. What I would personally prefer, however, is splitting everything else up as mucha s firearms are currently, which allows for a greater degree of character customization.
I noticed a few people here are in favor a big rewrite of this sort of thing, and since I'm working on just that, I'd really appreciate some ideas. You know, considering the thread I posted on the just that ended up being Austere responding to me responding to him responding to me for three pages before it died. But anyway, I'll be getting another thread up about that some time soon with everything consolidated.