I am trying to "upgrade" a speeder weapon to a light repeating blaster like what's on the Z-74 but cannot for the life of me figure out how, if at all possible. Can upgrade a light repeater to a vehicular weapon, but cannot upgrade a light repeater to a heavy repeater.
Also, it's not letting me remove a weapon outright, do disarm a vessel.
It only allows vehicle weapons for upgrades. I suppose I could add a check box to display non-vehicle heavy and gunnery weapons, but you'd get some weird choices. And there wasn't any "remove weapon" rules, so I didn't put it in.
From what it sounds like, you should probably just create new version of the speeder with your new specifications.