As for why the Empire don't and never will have the turret upgrade, TLT-Ruthlessness combo.
That's easy enough to avoid, you just don't give that ship an EPT slot, same as rebel Y wings, same as Punishers, same as K Wings. It's not uncommon for turret carriers generally not to get EPTs because Turrets are good enough that EPTs make them crazy. Notably, two of the ships in that list are TLT carriers.
Even on a double-attack ship I struggle to feel that Ruthlessness is worth the points; it's autodamage, sure, but it's autodamage that kills your ships if you're not careful, and you're usually more fragile than they are.
As for why the Empire don't and never will have the turret upgrade, TLT-Ruthlessness combo.
Maybe they'll have a Twin Laser Cannon you can stick on Vessery.
A man can dream. Double laser cannon would be amazing. WOuld have to cost 3 or less to go with TIE/D though. Which wouldn't necessarily be a broken price point if you keep it at range 2-3 only, 1 damage per shot.