Thinking about it further, I'd still like to delete the other quad(s) on the map, and add a megahealth in the hole down there with the quad. Maybe that's too mean. But it's easy to get out if you have the foresight to bring a grenade with you. And there's just too much humor value in seeing a blue guy trapped by his own greed and poor planning.
- well you can't make a wall into a ladder because that would require editing the face-flag properties for a brush. For the same reason you can't change textures or add/remove triggers and clipbrushes (in other words no geometry changes).