At 72v, there are 2 IGBTs available in parallel for the boosting. There are some very impressive IGBTs coming out:
IRGPS66160DPbF is evidently capable of 150amp at 50% duty cycle!!! It's in the SUPER 247 package.
IRGPS66160DPBF Infineon Technologies Americas Corp. | IRGPS66160DPBF-ND | DigiKey
There's plenty of room for the super 247 package, as there is 0.950 inch for each TO-247 (which means TO-264 can fit too).
So, the absolute maximum would be 300 amps in the boost section, but I think 200amp would be OK for short periods of time with the right monstrosity of an IGBT.