yeah most of my experience for level design is from kf/ut2k4... i wasnt thinking about making the trees sway using vertex animation, i was thinking static tree bases with texosc/pan leaves, so it wouldnt be too hard to spot snipers, but hard enough for them to have an edge at least.
plus i dont have too much experience with udk's auto-cull thing where it switches dist meshes to statics, again i was thinking of texture based obscurity.
edit-
once RS comes out (hoefully with sdk integration) i was thinking of making semi-contained maps, where you cant wander too far off paths into dense jungle, but i'll just wait for the release to see what i can do towards this idea, i'm just trying to think of how to make players immerse themselves in the environment, to be wary of the trees, in order for them to combine efforts when trudging through dense brush.
i have yet to be competent in udk, so i'm still not sure how culling works, versus in ut2k4 using antiportals/zone portals/bsp culling.