Okay, I can now confirm that the TIE Bomber is indeed activated by the switch.
It waits 4.8 seconds after the activation of the switch, and begins the animation.
After looking at the level, unfortunately, that entire sector is very large (takes up almost the whole pit) and is flagged for fading out (pit flag).
If you look ingame, the red striped texture on the wall (where a lift "runs along") ends at the bottom edge of the sector, near the very bottom. That is where the pit flag ends. As long as you don't reach the necessary fall velocity before the bottom edge of that red striped texture, you won't cause a fade out.
Also, the secret area Roy falls into is not marked as a pit, so achieving "pit velocity" won't do anything there either.
Finally, for reference, the start of the sector starts above Roy's head when he enters the pit for the first time at 0:16 (if you look across the pit you should see an edge, that's the start of the sector). The sector above is not flagged as a pit.
I'll look at the door next.
EDIT:
Okay, looked into this too.
The door is as you say, it will only open from one side (you must be standing in a sector on the opposite side of the door, and activate it). Once that happens, the door will open from EITHER side freely.
However, there's nothing in the code to stop enemies from opening it, other than plain AI stupidity (that is, the unlikelyness of them actually walking into the sector and activating the door). The enemies do seem to be spawned on map load (it's actually highly uncommon for enemies to be created afterwards), but I don't think any of them are really close enough for you to make them move. Ironically, the closest one is a mousebot, and I don't think he'll do what you want.
![:P](../../smileys/tongue.gif)