RE: Dx7 throttle kill switch
As far as Programming goes, the more higher end you go with the Tx, the more options for programming. You will see the same limitations with other manufacturer's lower end Tx's. Actually, the DX7 is closer to the middle as far as features and performance. It looks like Airtronics and Hitec are offering higher end Tx's at lower prices. There are probably others, as well.
I think Michael has found a way to use the programming you have to make the Throttle Cut easier to implement.
I train new pilots all summer long, on Tuesday evenings. The one annoying feature of the DX7 is the placement of the Trainer Switch. When using the DX7 as the Master, it is difficult to hold the Trainer Switch and still be able to control Throttle/Rudder, especially if you are teaching someone to Land or Takeoff. I would attach a wire to the hole in the Trainer Switch and bend it around the back of the Tx. That way, you can pull down on the wire to turn on and hold the Trainer Switch.