OP is 100% correct and any arguments against him are flawed. The correct move for the good of the game is to remove the upgrade entirely, and to remove the static resource generation from the base body as well.
Mobile, build-capable, self-defending units should not be able to produce resources, period.
The only, read, ABSOLUTELY ONLY reason it is even slightly acceptable on the ACU is that you only have 1, and if it dies, the game is over. That's the downside to a mobile, build capable, self-defending unit. Oh. No, there we go. There's the balance guys. If you want to keep the RAS SCU upgrade, the way to balance it is that when it dies, you lose the game. That might, maaaaybe, make it doable.
Anything else is not enough.
Remove the upgrade.