That's a brilliant list of improvements you have suggested.
I have some comments on particular features addressing your concerns. They may not be 100% what you are after but might make life a little more friendlier while we wait on further improvements.
Hide enemy players terrain from the Mini-Map/Update Mini-Map only when the region is currently visible through a scout or something like this.
I would really like to have this kind of feature or have it as an option available for custom matches as it would make it more unpredictable where battles will appear and how strong the enemy might be, what unit types he builds and all of that stuff.
In the multiplayer game you can set the Terrain to Revealed or Hidden. Revealed shows all the terrain (still requires LOS to see) where Hidden is the traditional C&C black fog which requires scouting to reveal all unseen terrain.
Allow players to see all selected units (for example a UI which shows: 41 medics, 2 dreadnoughts etc. are selected)
You can see this in the unit panel, it's pretty small though. Can't remember if it show's just the army or all selected units :/
Ability for dropped players to re-join a game.
Might be nice if for one player Ashes crashes or the internet connection is interrupted. Happened to me a few times while playing ranked matches.
There is a save game feature for multiplayer. Get the host to quit the match (quickly) then go back into custom match then select Load Save Game instead of creating a new lobby. Set the lobby to public and the original players can join. It's not 100% reliable but its there, and best to use the oldest save file as you new one could save after a player dropped out.
Allow to only select air or ground units.Just try to only select 20 small air units which fly over a huge army of yours. Good luck trying.
F3 selects all Air units on screen.
Does really the entire army has to turn around when retreating??Currently when a large army of mine with a dreadnought has to retreat as the dreadnought took a lot of damage I can rather let the entire army die then order a retreat as ordering a retreat would most likely cost me anyway the dreadnought and half the army.
Disbanding your army will allow for a faster retreat. Though retreating usually results is losses any way as rear(/side?) armour is weaker.
AI juggernautsDoes the AI even know what juggernauts are? I never saw them build even one of them (tested on Beginner, Easy and Challaging). This also occured to me when having build like 3 of them. The match is always over before the AI starts building them if it ever does.
Playing on Painful, the AI certainly will build Juggernauts.
Prevent armies from beeing formed on mouse click.
It really happens a lot when you don't want it to happen, even with engineers!
There is a game option for 'Quick Army Forming', try toggling that.
Don't play the same opening of the campaign 10 times in a row when a player failed 10 times in a row.
Holding down the space bar will skip through the opening dialogue in a mission.