typically IGH are not suitable for MTB type riding (jumps, shaking).
Maybe someone invents an apparatus to shift the chain to larger or smaller cogs on a cassette type device with multiple differently sized cogs. That way you don't have to swap wheels with different cog sizes anymore. i imagine taking 11 spare wheels on a ride and switching them out as needed for the speed and grade gets old over time. That apparatus would need a spring-supported cage to adjust the to different chain length needs for each cog. to avoid stopping for gear changes someone may add a cable connected to a shifter device on the handlebar.