If they can get a work visa they will be able to stay no problem. If not they will have to constantly exit and enter China, it will get very tiring for them... Unless of course SNH manages to do something
Travel visa and work visa are a different thing, and I believe Japanese passport holders can stay in China for 1-2 weeks without visa (been told so by Japanese friends living here). The laws for getting a work visa in China have gotten very tight, it's not enough to have a company willing to hire you, sadly...