Personally I find train signals to be fairly intuitive. The only problem I have is that one signal means the track is one way. In itself it is not a problem. If you have 1 signal on a piece of track, I would consider it obvious that you only want trains to travel in one direction.

The problem ...

If I had to design this:

I would separate the multiplexed signal using 1 combinator per item. Each signal would then be on a separate wire. We will then have a "list" of signals where some signals are present and some are missing. Since the item is coded as a number, the signal type doesn't really ...

Automated tanks!

I'd like persistent autonomous programmable combat vehicles which can follow basic commands like the trains do. Perhaps it could be done by placing a special part into a car or tank which can thereafter be programmed and be let loose to expand your borders. Bad programming leads to ...

It would make sense that uranium would not only be used to make power. Biproducts of the reactor could be part of the economy. A small reactor could become a requirement to make the more high tech things in the game. Because you are already building all the nuclear infrastructure, increasing uranium ...