The new supply system is not going to be a very complicated thing. It wont require a lot of micromanagement.
You can only build a depot (which costs 1 admin point in WiTW) in a named location on a functioning rail line.
You are already advancing your railheads manually by moving a counter. This is far more micromanagement then building depots.
Since you are already focused on your rail lines. When it reaches a town, you can build a depot on it (turn after it is converted). This will occur, at most once for every RR engineer you are pushing forward. But odds are you will build these depots in larger centers like Minsk, Smolensk...Kiev. Because the size of the depot is related to the size of the rail yard.
A rail line can only push so much freight down it. Freight is Supply/Fuel/Trucks/Replacements.....the whole enchilada. And if you use that line to rail units....that will subtract from the amount of freight that will move along it.
Units will be supplied by depots. It costs truck movement points from the depot to get to the hex adjacent to the unit. So at the most, you can supply a unit 50 hexes away from you depot....at an increasing amount of trucks (including wear on said trucks, and fuel used by those trucks)
There are some ways of controlling this flow using supply priority at the HQ/Unit level, and you can do the same at the Depot level, although I doubt that will be a problem. The rail lines themselves should be the bottleneck.
Note: this is all from War in the West, and they may have changed things for the Eastern War.
There are no HQ buildups in War in the West. Supply is easy to track and watch and at its simplest level requires you to only build a depot in a town every few turns in the beginning of the game down a rail line.
The amount of trucks is something to keep an eye on, and will require some thought as to balance between freight movement and motorizing land units.
Compared to the problems of invading a continent....repairing ports, building new depots and pushing through France...Russia will be a breeze for logistics.
“My logisticians are a humorless lot … they know if my campaign fails, they are the first ones I will slay.” – Alexander the Great