Hi, Derek
There is no reason I can think of why Vietnamese would not work if Chinese does.
However, if you want to be 100% sure, there is no better way than an actual test.
1. Create a new v16 DB. Make sure that default collation is UTF 16.
2. Take the existing v10 DB and unload it into the above v16 DB.
3. Try to view that data in the new DB.
If you see the data correctly, then you would have just made a scientific proof that the upgrade will work.
If you do not, then please, report it and we shall see where the problem is.