This is what I suggest:
Instead of having an on/off toggle, have it be an on/off/chain toggle. When the weapon group is fired, every weapon that is set to "on" fires the whole time, and every weapon in the "chain" setting will alternate as usual. The backspace command could still turn chainfire on or off for the entire group, and the new 3-way toggle could then be used to fine tune it (or someone could just do it all with the 3-way if they weren't in a hurry).
Edited by Theevenger, 06 April 2013 - 08:25 PM.