If the game is Gen2 (or some other C&C with worker style construction) then I think the following method would be pretty good.
Basically, there would be a 3rd resource in the game aside from power and credits. That 3rd resource would be building supplies. Now I realize Generals used Supplies for their economy, but these supplies would function separately.
Basically, the construction yard would hold onto these supplies and your workers would have to commute back and forth between the construction yard and the building site. What this means is that apart from how large/important/expensive the structure is (larger structures would take a longer time to build), the further the structure is from the construction yard means the longer it will take workers to commute back and forth with supplies and the longer it will take the build it.
This means that if you want to make a structure far away from your main base it will be much harder and much more risky. You would either need to pack up and move your construction yard (if it is mobile) or create a new supply depot (new structure to hold supplies, similar to Tiberium/Ore silos) where workers could get supplies from closer to the construction zone.
-Adds a new resource and structure to the game to make it fresh and new.
-Allows players to use more strategy when constructing their base.
-Adds a new resource to the game and thus more strategical weak points for your opponent for you to harass.
-Makes early game progress much faster. Structures will be built in closer proximity which means their uses will be available to the player much quicker.
-Would theoretically make expansion bases much more effective than they would be if there was no drawback to building far away.
-Makes it more risky to build spread out structures.
-Commuting workers present a vulnerability if you don't have the support units around to defend them.
-Makes the main base of each player easier to destroy since all the structures will likely be very close.