Ran around TT in an M8 for awhile just now. You don't make it easy to sneak up on the GV bases in a GV. And much of the high ground is bare leaving you to expose yourself to shoot down at the bases. Same thing for the high ground on the TT object. But the trees are thick enough that moving will make shooting at moving vehicles problematic even with a good sniping position or a good hide. So moving inside of the tree line will become s.o.p.
I just had another look at this. The V bases in TT are all the new 2 mile square type. While I can alter the underlying texture around the base to whatever I like, i.e snow, sand, forest, the terrain elevations and the tree placement within that two mile square are part of the V base itself.
The only thing I could do to increase the cover would be to replace the two mile square V fields with one mile square V fields, that way only the last half mile of clutter and elevation into the base is controlled by the field object's clutter instead of the last mile. I am not sure that I want to do this though, as I quite like the idea of the TT bases being hard to sneak up on.