Trucks Can Build Roads and Upgrade them to Train tracks

Roads Offer a mobility discount of 20%
Train Tracks offer discount of 40% movement cost

Anyone can use a road or rail after its laid

Improvements can be destroyed as usual.

have fun micro-managing the build of those. i'm going to save my wrist from that.

Manual construction and use of transportation infrastructure would also likely hamper the kind of cross-continent army shifting it would be meant to alleviate by interfering with perpetual moves. I would rather see a simple movement bonus inside friendly areas.

Having a perpetual road/rail placement option for trucks would not be out of the question. Its essentially another type of perpetual movement just for trucks. Maybe at 1/2 movement a truck could put down 4 road/tracks

but I could see this more as part of a version 2 game where true terrain is added to the game

ie
Mountains (impassable)
Hills -1 move
Swamps (1/2 move infantry, Jeep/tank Impassable)
Grassland (normal movement)
Roads 25% move bonus
Rail 50% move bonus

Trucks could do the following
Turn Swamp to grassland
Tunnel/blast Mountains
Grass/hill to Roads
Roads to Rail

Option wise for movement just add a couple types of improvement (full or partial) w/ perpetual to truck options

I suppose you could just make it a simple option by allowing any units to move, not just those on a Land Base.

This has been brought to the table about a dozen times.

Variable terrain moving interferes to much with perpetual attack. As someone who played long before perpetual attack, I can honestly say it was the single best addition to this game.