I had a few aha moments today.
Construction. I’ll use a variable construction rate. Basically everything will have a number of resources required and a maximum construction rate. In addition you’ll need the factory which can only burn so many resources per period. The lesser of those two rates is the applicable value.
Dawns on me that while most players will want faster games (ie more shooty less thinky), I might be able to do all right with the niche.