I believe they will as long as it is proven authentic. I have seen people buy preloved luggage pieces and have then heat stamped the luggage tags. Should be the same concept! Good luck!
Yes, my SA was discussing this with me the beginning of the week. He had asked if I had ever thought about getting it done on my bags. As long as they are authentic they will do it for you
Be careful. They just ruined my husbands new wallet when they did a horrible job heat stamping it. The monogram wasn't centered or even do they are getting him a new one. Not sure what they would do for you if the bag wasn't brand new. They don't often admit fault.