Actually if you can pick up an 0411 from a salvage yard that wouldn't cost very much, as you said earlier it is documented how to make one a stand alone trans control. All you would need to tune one is a obd dongle that interfaces with ls droid or pcm hammer and use universal patcher,
That would also give you a towhaul switch cabapility
You still need crank sensor and the 4x signal would not be difficult to fab. I seen a post on 4bt forum years ago a guy made slots in a pulley and mounted a sensor near it. It doesn't have to be times right, just needs to give rpm signal.