While this fix would probably be fine, I disagree that VTG with the current ruling is nescessarily broken. Yions doens't do anything that's not a core part if the game: it points at things, shoots, and takes damage in return. That means it can be costed correctly. It's probably a little bit too cheap right now, but that doesn't mean the mechanic can't be priced correctly.
I understand why you might want a cheap gunner for turrets without front arcs, but all upgrades has to be costed according to it's most effecient use. Simple variable costs are nice, but Shield Upgrade is still not worth it on Academy Pilots. We have to accept that some uses of all upgrades will be bad. I like there to be a reason for Y-wings, etc to have their turrets in the front, but if we want to keep that, we should hope for a new gunner for "true turrets" instead of making it this one.