I would replace Mech Assault with Lightning War personally. You have loads of early game options and appear to be a very aggressive player. However by only having doctrines in your loadout that cater to the early game you take away your ability to have a sufficient late game.
Lightning War includes
Jaeger Light Infantry upgrade: which is cheap and makes Grenadiers very effective and all ranges, but especially as close range. It also comes with the rarely used interrogation ability which in the grand scheme of a battle is useless, but in the final push to destroy the enemy and win is invaluable.
Relief Infantry: Allows you to get some tasty osttruppen to help cap up the map and finish the enemy.
Tactical Movement: Used for the same purpose as above. Makes troops move very fast, but can't fire while sprinting.
Tiger Tank: Self explanatory heavy tank, good for closing games and spearheading assaults.
Stuka Close Air Support: Nerf slightly a few patches ago, but still a beast of an ability if you have LOS and the enemy lacks AA (Which they usually do).
That's my case for Lightning War. Other options would be Spearhead Doctrine and Assault Support although the latter of the two is a lot less competitive.
