The 50 MHz band is right on the boundary between HF and VHF.

Now it can't be allocated as a Downlink since it isn't allocated to the Amateur Satellite Service but what about an Uplink in that band ? It would operate in a similar manner to OSCAR-7 Mode B which has a receiver outside the ITU allocated Amateur Satellite segment.

A 50 to 29 MHz transponder would be good.

ITU WRC-19 will have an Agenda Item for a global Primary Amateur Allocation at 50 MHz. Unfortunately that is for Terrestrial only not Satellite but arguably that wouldn't prevent an uplink receiver being flown. Clearly worth lobbying ARRL and IARU to work towards getting a Satellite Downlink allocation at 50 MHz for future sats.

73 Trevor M5AKA