Yes, the idea is really good. But what i would advice to you is drones.
Gunnery is quite universal weapon skill, so it can combine with any weapons. So how about a SmartPlatform, or rotodrone, or duelist, with a weapon of choice. A sniper rifle, shotgun, smg, assault rifle. But, it will hurt a lot if it will get hit, and you are inside. You can not slave it to your persona as mancers can not have a PAN. So you should not let drone get hit. How about a sniping position, so it can give nice fire support to the team. [You will get some bonus for HotSim, etc.].
High fire wall means high WIL, means high fading pool, so your next best choice is to use complex forms a lot. But here the mancer problem arises. All mental attributes are good for you. If you want to brick weapons or other electronic equipment you'll need high CHA, for attack limit. Or you could use pupeter, or resonance veil, if you have big imagination and a nice MG.
Just remember, all things in 2072 is online. Deck, Gun, Pants... But the gun, even if not smartlinked, have wireless capabilities, so:
Use resonance veil to 'make the gun think' that it is the time for regular maintenance. You don't need any marks for resonance actions anyway.