Agreed that most constructors fall into the design of "best single engine, no life, no sensors, max constructors", but there are scenarios where you might not want to follow that design:
-starbase is in contested enemy territory, where more engine speed drastically improves its chance of survival to the starbase.
-the shipyards near your starbase are soley focusing on military vessels, and the only avail shipyard is very far away, hence you might sacrifice 1 constructor for more engines
-you may only need 1 constructor for a very long time (a single SB scenario, not a cluster of SBs in which a multi-constructor is often used)
Granted, these still are not the common use. Perhaps allow one to select as I have proposed, but also allow an option to disable this per starbase and select a "preferred" constructor design. The preferred constructor selection would be an empire wide decision, not a per starbase decision.