I would book the economy or premium economy award tickets and cancel if/when affordable business class seats become available.

I am assuming that it is still true that the miles will be instantly redeposited upon cancellation. The only thing that gets locked up is your ability to fly home on the flights/date you want, albeit in economy.

Looks like it would 100K milles for jp to usa biz class with United miles for a United Visa cardmember.

ETA: it might actually involve changing your existing tickets, but pretty sure it is cancel and rebook