I have a SMPTE to MIDI Time Code converter that I would use to record a SMPTE stripe track on the multitrack recorder. Then when I played it back I would feed it back into the MTC converter unit that would then drive my keyboards so I could always record keyboard tracks individually. That would let you do exactly what you want to do.

The unit I used for this was made by Anatech back in the 90s but it looks like JLCooper make something similar http://www.jlcooper.com/pages/pps2.html
It goes for about $305 but it would let you record exactly like you would want and you would still be using it years from now with whatever multitrack and keyboard you are recording with at the time. I still use my SMPTE-MTC converter after 15 years so you will get good value from it.