You can use func_clip_vphysics to block specific projectiles only
Make 2 filters, one that blocks tf_projectile_pipe and one that blocks tf_projectile_pipe_remote, and use a filter_multi to combine them, and set this multi filter as filter in func_clip_vphysics
That way any stickies and grenades will bounce, but any other stuff like rockets, bullets and players will go through
Alternatively you could use func_remove instead, in which case the grenandes and stickies won't bounce, but disappear completely
@ABS, are you sure that displacement method still works? I tried that a while ago and it wasn't very reliable (players could get stuck in it, and some things in your list still wouldnt go through it)