I have been following this email chain, I have a T2 control on a VMC100 with a floppy drive. It has never worked and I am curious if this is a similar system to what you have.
I ended up taking a microtape drive unit from a backup t2 control I had and have been running that. I really don't care much for the tapes though and I only have 3 of them.
I will say I was able to plug the tape drive in and it worked right away. With that said I also installed the CPU board from the old T2 I got the tape drive from as the main CPU has some bad interface circuits. Changing both items may be why it worked so easily.
I do recall the original CPU did say Disk for saving and am pretty sure it now lists tape, but I would need to confirm. I am not sure if there is an eprom change other than the "Disk/Tape" change.
I would like to revisit the Disk unit depending on your results. I will continue to follow and will locate the disk and controller drive this weekend to confirm some of the information on the unit I have.