I'm not sure it would even matter. VP candidates don't usually bring much to a ticket. Mostly they bring vibes. Well, he already brought the vibes. I don't think that Trump can run away from that, even if he were to replace Vance.
Also, now that the convention has passed, it becomes considerably more difficult to replace Vance. They would likely have to take another vote of delegates, which might or might not be easy depending on whether their term has expired. Plus, they might have already submitted the candidate names to various states, which right now is probably quite easy to fix but gets harder in a little while.
In other words, I do not think Vance gets removed. It would also potentially alienate the Silicon Valley folks whose money was the reason Vance was picked in the first place.