I don't see why being time-critical should be the only governing factor.
I guess all this calls for tertiary and quaternary fire buttons, which shouldn't be too difficult to integrate into the outer rings of the current HUD design.
I think it would be good if all (most) things were bindable. There didn't actually have to be the concept of additional fire buttons. Bindings would take care of what was needed.
I do understand the point about the way the HUD is shown. However, I currently see things like chaff and heat sinks on my HUD and I have never set those in any firegroup. Since they are bindable, I bound switches to them.
Toggles for KWS and the various DSs would be good.
1. You could avoid going to a different fire group
2. Holding down a mouse button for 10 seconds can lead to finger ache !