Okay, a lot of the comments here have been talking about early era (typically Ancient and Classical) improvements and refinements, and Zappara made it rather clear that he's looking at improving the modern, transhuman, and future eras primarily with the release of 2.8. Maybe we should try to give him a little bit more help there?
I will admit, I'm a little uncertain what to suggest right now, given that you're still keeping the promotion lines secret.

I already mentioned the info combat promotion line in another thread, and you implied that you're working on something like that already. One other thing I would like to see is that more of the specialized modern era units can promote to some kind of futuristic unit. Guerillas and special forces won't just be phased out of combat tactics. They will likely play significant roles in human conflict for the forseeable future.
With this in mind, I would like to see a few 'low tech' units maintained into the future eras. I use the phrase 'low tech' as a relative term here, of course; we're not talking men with clubs fighting assault mechs or Dropships. The EMP Infantry are currently the closest thing to what I'm talking about thus far. They are designed to excel against the more mechanized units through specialized tactics and equipment.
Other than that, perhaps the modern era can focus on refinements of older era buildings, boasting slight improvements at a small maintenance cost? For example, a Butchery could be replaced in the modern era with a Stockyards, providing a slightly higher food output per available resource, but with a +5% or +10% maintenance increase to represent the kind of infrastructure that the government needs to put into place to make such modern processing systems work effectively.
One last thing I would like to request, and I don't know if this is something that you can do in RoM, or if it's even an option in modding at all. With the amount of modifier bonus you can get to production output, letting 'overflow' production be increased by the modifiers as well is ridiculous. A city with, say, a 50% production bonus winds up with 20 hammers in overflow. 6 of those hammers of overflow are directly attributable to the production bonus. When the next turn comes and all production is boosted again, the 20 hammers of overflow become 30 hammers production, even though 6 of them were already the result of the previous turn's boosting. Is it at all possible to make it that overflow hammers are added to production *after* all the percentage modifiers are already added, in the way that food is added to production without any modifiers for Settlers and Workers?
That's all my comments and suggestions for now. Keep up the fantastic work, Zappara. I'm looking forward to what 2.8 has in store for us.