ast minute requests may be acceptable in China, but acceptable to Westerners? Not for me, not now, not on my watch, not ever!

Exactly. The shameless self promoting that the locals will heap onto you without putting your time into consideration is pretty bad. Wasting so much energy on things that you did not have any say in will drain your spirit and make you lose hope, affecting your teaching quality in the meantime. In China, people are not treated as people, but merely as a disposable economic unit to be drained and used up as seen fit by the folks with status and power. Until this is corrected China will continue to be seen as backwards and rightfully so by the parts of the world that are more civilised.