I think that when you leave a teleporter all destructible props should be destroyed, and weapons/items don't cause a telefrag.
Agreed. I believe spectator props as well as props positioned by players should not determine whether a teleporting player should be killed, let alone a traitor attempting to escape from crime scene.
Instead, how about a small pop-up indicating the location is blocked? "eg:
Teleporting failed, location is obstructed!"
It would help.