Footprints and Tread-marks in Specific Terrain

This could add a whole new level of subtle but important strategy, if ground units were to leave their "footprints" or tread-marks in certain terrain, like mud, sand, or snow, etc. but not rocks, metal or shallow water obviously.

Such evidence of their passage should last on-screen for a short duration, roughly equal to the average amount of time a unit takes to cross an 800 x 600 screen.

Anyway, this could bring an interesting element to raids, where the attacker has to take care not to cross through any terrain which would give them away, in order to retain an element of surprise.

Now, the immediate problem with that which I can think of right away is the excessive stress it could place on low-end systems, with, say, hundreds of Zerg units moving around. Obviously it can't be made just an optional graphical detail, either..

Another concern would be cloaked units, like Protoss Dark Templar or the Terran Ghosts; should they leave footprints? Maybe they should, but only for a lot shorter period of time, like a second. and what about "hovering" units, like Terran Reapers, or the workers? Maybe Reapers and SCVs could leave a little "burn" trail on the ground resulting from their thrusters, and they'd be unique in that they'd leave an imprint on metallic (i.e. Space Platform) terrain as well, but Zerg Drones and Protoss Probes would leave no traces.

What do you think? Combined with the new Line-of-Sight and Elevation rules, Footprints could let terrain become a very important component of overall strategy.