Good idea. A vehicle that will blow smoke in the radius will make a shadow mark so that the  enemy won't spot your units. It would probably be more useful for forest terrain.

It's a good idea but the if the smoke shows the other player will know that there is units hidden there and you can't see the enemy as well because of the smok but good idea 

That’s a great idea ,

also allow artillery and tanks to do this along with ships and planes. (as in scouts dropping smoke from the plane as they did in WW2 for target identification.)