Repair turrets are a good solution to bridge the time until you can build roboports. But therefore they should not be THAT powerful. They should only have half of their range -maybe being upgradable- and only be limited to do repairs, no constructions. In principle, they would be still even in late-game a good alternative for roboports, even with only a 12-field-range but enough repair speed. A smaller effect area would be also an advantage for turret phalanxes.
