HAMMOCK?! WHAT D'YA THINK?!
As you suggested its hard to reach for the attackers being up high. Offence can get up there by running up the wall, engi finds it hard, a waste of a rocket/pipe (health) for solly/demo but hws cannot get up there at all.
The tunnel itself is pretty damn narrow so it shouldn't be hard to defend should anyone come down...
All other changes as suggested in this thread are done except for on screen notifications for "you must capture point XYZ first!" when in an uncappable trigger.
I need to commit it to beta and get testing on it now - but I dont think it'll be a problem.