I have a couple of suggestions based on my thinking about where things are going in the 6 powers campaign:
1. How about something like an "Improved Engineering Section", and Advanced, and so on. Each would be the same size, but would offer improved function.
2. This one is somewhat tricky. An "Automation" tech field, which could work one of a couple of ways. On the one hand, it could reduce the population required for an installation by a fixed percentage, say 5% per level of improvement. So a society with level 2 in Automation would only need 40,000 pop for a mining complex. Or, on the other hand, each level of automation could reduce the percentage of the population required for service and food production, thus effectively increasing the productive population of any given population.
Kurt