Let them remove Xbox Live and Twitter in Chinese markets, give them their own shade of live tile. Stuff like that I could care less about. As long as they are not permitted to install ANY bloat/crapware that cannot be deleted or make any changes to how the GUI works, especially changes which could affect performance cause any graphical anomalies with other apps or delay OS updates.
Anything like that which treads into Android territory is unacceptable. Skins should be verboten, of course, that should go without saying. The minute Microsoft lets someone skin WP8 or install bloatware you can't delete, then WP8 has "jumped the shark" as they say. It's too slippery a slope that leads right into a low quality Android-like user experience, and then I'll be going to the Apple Store for my next phone. Don't do it Microsoft.