Can I replace the purchased products with my own brand or trademark for re-export?

Answer: No, this is illegal

"The People's Republic of China ***Article 52 of the Trademark Law of the People's Republic of China: Anyone who commits any of the following acts shall infringe upon the exclusive right to use a registered trademark:

(4) Changing the registered trademark without the consent of the trademark registrant and Putting the goods with the changed trademark back into the market;