1) The need for this has indeed increased since (heavily damaged) units don't merge anymore in 1.5. It is a very old suggestion, but there seems to be some problem on the dev end. Same for disbanding units, btw; we are currently stuck with heavily damaged units which are useless but keep eating daily supplies.
2) The terrain is actually displayed quite clearly in the client?
3) This is already available if you take a subscription to High Command. Devs need to eat, you know.
4) A nice suggestion, though I would personally be very hesitant to pass control of my precious units to the AI. It shouldn't be too hard to implement; all that is required is a control "Put me in inactive mode" somewhere
5) This has recently been improved, so rebelling provs don't go to some distant nation anymore; control will always be passed to "someone closeby". It works fine now, I think.