In small numbers these people are useful, and serve to entice and confuse their compatriots back home. As long as local society is cohesive and there are laws that come down hard, these sporadic additions can be controlled.Gonna play devil's advocate and post something people might feel uneasy about. It has nothing to do with the video, which I've not seen.
When a Chinese person betrays China and goes to a rival Western nation to badmouth it, we say this self-hating hanjian scum will never find acceptance or respect in that society but be viewed as a jester or dog huddling to please a master.
When a Western person or a person from another hostile nation to China moves to China applauding Chinese society and swearing allegiance to China over thier native country, what do we call them? Are they not the foreign counterpart to the hanjian we just discussed? Do we accept them as Chinese because their words and actions please us or do we look deep into the character of a traitor?
Personally, I don't respect anyone who doesn't show self-respect and self-love. A foreigner in any nation should maintain the dignity and honor of one's own native country at all times and at best, in the most friendly of situations, open a second place in one's heart for the culture of the adoptive nation while saving one's sacred place always for one's own culture. It is a matter of character and quality that no one betrays his nation for a hostile nation; I never trust or respect people who do, even if they run to China's side. Because if they betrayed their home country, how easy would it be for them to betray mine when the convenience arises? My motto is, "If you're not welcome in your own country, you're not welcome here either." It's placing the caliber of the individual over what is personally pleasing to hear.
I would not want large numbers of seemingly 'patriotic' foreigners swarming in; look at the US with the Indians who later form their own Hindu caste based blocs.
I think Korea can be assimilated over time through a bit of tough love (funneling pride to be part of the greater Chinese identity, post liberation of course), given their weak cultural underpinnings, but the Vietnamese would be a harder nut to crack.
If Japan is split and assimilated piecemeal then you could easily incorporate Okinawa, and Hokkaido (through emphasizing their Ainu foundations).