I haven't been to Beijing for a couple of years but Sephora is in Shanghai and certainly the luxury brands are very well represented in major cities so the likes of the Hermessences line and so on are there in the flagship stores and boutiques. Maybe some basenotes buddies in SHG will pipe up regarding the mail in/out thing but I know they rely on Hong Kong for some purchases - the prices are about 30% less here than the mainland.
I did some investigating into vintage perfumes in Shanghai (it was once 'The Paris of the East') and while I found a few lovely old botlles from the 30s I'm afraid the intervening years seemed to have laid waste to any hidden treasures from that era. I doubt there is anything much around older than a decade or so, from the early 90s when commerce started opening up.
Enjoy your stay there - maybe catch up in HK