Maybe the short range is to make-up for the fact that they can put them away on command, where no one else can.
As for OKW stopping m20. Yea you don't get a teller. A schu-mine does well though, you just have to follow it up if the USF bought armored skirts. Without the upgrade I think it 1 shots it, but I haven't checked yet. Shouldn't be too hard since you have about 4 or more different units capable of finishing it off.
There is a really strong mine that is in the game files for okw, but it doesn't seem to be in use right now.
