Hardinge KL-1

[EddyCurrent]

then this will connect into two of the connections of a 3 phase input VFD.
I'll common up two of the inputs to share the loading on one AC cycle a bit more across the VFD rectifier diodes.

I've never heard of this done before. Devices inside the drive use a particular phase for synchronisation, that's why they specify which terminal to use if you are on single phase input, also a 3phase rectifier relies on phases being 'out of phase' for the return current but 2 of yours would be 'in phase'.
I hear what you are saying about the original motor but to be honest a modern 240v 3 phase motor is going to be just as good, the 240v drive will be cheaper and you won't need a transformer.