Does he also appear in the game as a playing character. meaning a character that you can build. Play as urself. Can you build a General character at the barracks and can he support his own troops by assisting them onground ?

As example called "Hero Units" in C & C

nope... No such thing in game.
Just the units in your battalion(u are a colonel so... no generals except those corresponding to the factions- Mitchell, Izotov and the European guy whose name I can't remember)

nope...no hero units...