I don't mind this for setting up an initial station, but sooner or later in any system I'm going to end up with a bunch of T3 points, and with all the facilities I'll want to build, crucially not enough T2 points to just put a coriolis in the slot I had pegged as the ideal site for a large orbital, and the only things you can build with T3 points (which you've presumably built up the system to obtain) require north of 200kt of stuff.
The way I see it, there's two broad types of solution for this: passive and active.
Passive: building up your system's economy causes it to slowly contribute to any open construction projects over time, in some way or another. Maybe something like having economic links connect to the building site and supply its commodities or something.
Active: have literally anything other than hauling contribute to the construction sites once your system is established. For instance, if economic activity in the system also contributed to construction progress at a rate of, say, 1t per 100k of base mission reward or trade profit, then a max-reward 50M mission would still contribute less than a single cutter-load, but it would happen in the background while people do other stuff in the system and the cumulative effect of a decent number of players simply passing through the system would chip away at the sites over time.
...