I like the idea. But I think that most people wouldn't bother learning how to hit the coordinates exactly, especially with alternatives such as camera-guided and laser-guided missiles.

if a scout marks a target all players should see it on the playermap,  not only the commander  

well, thats only possible if we make some special trees, like a building (Tower) with a invisible ladder and a also invisible plate on the top!

these tree was extrem diferent to the other trees, and there for i think it´s not so an good idea, cause everybody knows it!

Maybe the idea for itself is good, but impossible with the normal trees!

People would still easily recognize the trees that were custom-made for snipers and just blast away at those.
Sphinx Studios doesn't have a problem creating climbable trees, but with their inevitable uselessness (there are no trees wide enough to have a [hollowed out or not] room for a ladder, an entrance to that ladder and the player itself). What's a hideout that everyone sees immediately?

Could you make a gun with a grapling hook? Also could a soldier be made to lower a rope over the edge of a bridge or clif and climb down it?

we want this in OO also but it´s still impossible in the moment!

Graszwang!!!!!!