REPLY TO MY OWN POST:
In case anyone is interested. The switches can be SPST. There is no mechanical interlock - DUH! Logic controlled; and done very nicely by Otari.
The choice of RJ-45 was not an option - I needed a minimum of 12 wires to provide the remote functions needed.
The LED retrofit was easy. I pulled all the incandescents and replaced then with off-the-shelf LED's. The only tricky part was the current limiting resistor installation. If anyone is interested I will provide the photos of the procedure.
The remote control was not so easy.
Step 1: I used large "video game" type switches for all the functions. The switches selected allowed the installation of back-lit graphics of the control functions. I had originally labeled these switches "STOP, PLAY", etc. Poor choice. A much better choice will be arrow graphics and industry standard for tape motion functions. Will upgrade next time I print labels.
Step 2: Otari only provided for one indicator light - RECORD.
I felt that all functions should be indicated by illumination. A quick check of the schematics will reveal that all the functions can easily be indicated by pilot lights except the function "STOP"