This is a completely hypothetical question - I haven't even finished my manuscript yet.
I'm just wondering if people would be willing to change the ending of their novel if a publisher asked them to or would you want to keep the original story that you created?
Absolutely - If I had written something I wanted to be accepted into a commercial market then I'd happily review any areas asked of me.
Really good question!
From what I hear agent-editors and publisher-editors will often request changes that have a global impact on a piece of work. Of course their requests are more like demands, and it's up to the author to decide if they want to listen and make the changes, but these are professionals and should know what they're doing so the changes are designed to make the book stronger and better.
Making changes does not mean giving in to artistic integrity and as authors we should always strive to improve, and if professionals try to help then listening to them would be a good step.
I'm 100% confident I would never let another person interfere with the ending, after I have done everything I can on it and I'm happy with it. But if I am given a decent idea or a better one than the one I have, I won't be hesitant to use it- that is of course I personally like it and think it is better.