I was thinking the same thing about "trade routes" when I started reading this thread, as the constructor micro-management can be a pain for me as well.
The nice thing about making constructors like trade routes, is that like trade routes, they can use similar mechanics for revenue! ...albeit a negative number

Think of it, your constructor "route" costing 8bc a turn (avg) to maintain / steadily upgrade the base. If the designers had it so that each time the mini-constructor reaches the base it gets an "upgrade" we can have our realism and eat it too!
If your constructor had multiple construction-modules, you would get multiple upgrades each time the mini-constructor reaches the base
The more costly your constructor (because of extra modules/engines/etc) the more the route would gut your economy per turn... This "cost" would equate to what it would normally cost for you to build/produce/buy another constructor (or some meaningful factor of that nature) over the course of it's round trip
And if you want to send multiple constructors, and establish multiple routes, you could.
Hell, you could still build uber military bases in a single turn with the equivalent number of constructors under this system, same as before... just be sure to 'kill' those 'constructor routes' lest your economy take an unwanted hit
And if you kill an enemy mini-constructor, perhaps it could be coded to immediately 'kill' the route, so as to keep with how things work currently.
...
Only thing bad about this idea, is that I would REALLY need to remember to name my bases something meaningful, lest I forget the intended purpose of "Military StarBase 0568" ... I mean, was that the one which needed the ray shielding or the atlas sling? I can't remember!