Once someone signs up, they could state where they're from, and either try to pair EU vs EU and NA vs NA up until the final as much as possible, or have separate brackets and separate prizes for each. Otherwise there's going to be a lot of missed matches like this round in every tournament.
Another solution is to extend rounds until the weekends, but as we have also seen, BR's and other tourneys get in the way too and is no guarantee matches will get played.