Would it be breaking for there to be an upgrade that allows a ship with the double turret arc to, once , fire two shots in the same arc. It would be limited to one of the two arcs already covered, and explicitly state that it’s charge can’t be regenerated. Maybe even add a stress.

In some ways, even if on a 4 attack ship, I can see this not being a heavily used upgrade, for many would prefer one that isn’t a single use, but I can also see the potential problems.

Thoughts?

Probably, yes. We've seen from Dengar/QD just how powerful the double-tap effect is, and if you had it available to use at the point of maximum advantage, rather than dependent on opponents actions triggering it, you'd be winning games with it all the place.

It'd depend on point cost, opportunity cost (what else could fill the slot, like Ezra if it's a gunner), what ships it can reasonably go on and what the downside is (like stress, ion etc).

In 1.0, I'd gladly pay 5 points for a double-shot from Dash's primary arc. I'd pay 6-7 for a double shot from something like a Ezra/Maul Ghost's front arc. I'd pay for a 0 point turret upgrade that let a Y-wing double-tap once out its front arc.

In 2.0, there's serious action economy in performing an extra attack - especially if that attack is modified by something like Predator. It's the sort of thing that'd have to be priced way too high for competitive use, or would otherwise be meta-defining.