True, but it's so annoying that I can't stack even two military units together. Not only does it make defending siege units on the move harder (as they have to end the turn on their own and almost defenceless), but it can make moving even a small number of units a real chore. Technically it should make for a more realistic experience I agree, but in reality, it just becomes a pain in the arse.
As for obsolete units, yes I can upgrade them, I just feel that it would be nice to have more time to use them in each era, rather than just getting in a rush to mechanized infantry and modern armour
There's lots of little things that I wish had been dealt with too. Unit escort for instance - this is especially important now that units can embark and are defenceless while doing so. Further to above, I think limited stacking should be possible, so I can tell a destroyer to shadow the embarked units and protect them. Units cant be grouped so it's a complete faff having to order each individual unit to the same location, especially when other unit orders aren't displayed.