If they're from the poorest parts of China, their wealth would just be comparable to Ukrainians, which wouldn't be enough to settle properly in western countries, especially not when they need to overcome language barrier.Export them to western countries, via targeted advertisements and incentives. Too early right now, but once the overall competitiveness of the country rises, and these leftover men get a fighting chance overseas, they can and should leave in droves to those destinations.
Better for them to go join/create firms/projects in the third world, which I think is what a lot of people from the poorer parts of China are doing already.
In practice very few Chinese people would ever struggle with there "not being enough women", that's apparent if you've been in China. 90% of youngsters move out of poorly connected villages for a reason. If you stay behind, it means you want to keep doing your thing out of tradition, when you can either go to a city or even to another country.
But China should also encourage these holdouts to go other places. Spreading controlled immigration is also a soft power tool. Just look at how many overseas anglos there are. A bigger Chinese presence in the third world is needed.