Developers in HongKong are ok too if they employ developers with mandarin Cina skills
We have a few chapters in Mandarin in one of the books. FileMaker coped quite well, I did not notice any problems. Fonts mostly worked, occasionally you can get hieroglyphs replaced with squares. The character info still retained and they do work after export. There was something with the field setup in Storage/Language. All fields are set to English by default so some searches stopped working. I tried to set the fields to Chinese, but ended up with Unicode in the end.
We import from SQL Server using Stored Procedures, so a lot of varchar variables had to be re-written as nvarchar.
As far as I remember, there was a problem with the field export, which is UTF-16 by default and we needed UTF-8 for our workflow.
So, the problems were generally not with FileMaker but with integrated system around it.