Earth 2150 gave you a home base in which you could build news units, research new tech and so forth both in between individual campaign missions, but also right during the missions themselves.
As a matter of fact, you usually would start a mission by loading a small strike force of your prefered units into a transport shuttle and sending it off to the mission area. When the job was done, you would subsequently pack your boys back into the shuttle and fly them back to your main base, because the game had a (however simple) experience system and all units still on the map when you ended the mission were lost permanently.
You theoretically could also build production structures in the respective mission map itself, but given that the entire game was built around harvesting as many resources as possibly before a timer (and your lifetime) ran out, this was something you generally avoided like the plague.
Earth 2150: Lost Souls actually attempted to establish a similar system for the AI, but sadly this only meant that the AI would regularly get free units in a campaign that already was tough as nails.