Sending passport to own country for a new visa - How about problems with leaving China after that?

Hello, I have a question regarding sending passport via courier to the agency in my own country to obtain new visa, while I would stay in China.
Some friends told me that it is very risky because if I get a new one, there will be no entry stamp, which is normally given when entering the Chinese border. So how about when I would leave China somewhen after that? I will show my passport in the immigration at the airport ( In my case also newly issued passport) with a new one but without " enter stamp" , so how they could give me "leaving stamp" on it? Of course my previous " enter stamp" would be in my old visa ( and old passport), which will not be valid until than. Is that possible? Some people told me new visa always need to have " entering China stamp"

I hope it was clear enough what i wrote above. I would be very happy for any answers and help, because I am really running out of time