The rules can be ignored, but the rules do exist. Legality only ever matters to the extent that anyone enforces it, but breaking rules doesn’t make you look good, and donors may not be excited about supporting an organization that won’t enforce its own rules. If they do want to replace Vance, they’ll pressure him behind closed doors to resign, not make it a spectacle. I’m just pointing out that if Trump could openly fire him, he’d probably have done it already because Vance is making him look bad.

I agree that whether the VP matters is very questionable. Bottom line is that if they think Vance is enough of an election liability, they’ll get rid of him, but it’s entirely possible that it won’t make much difference either way.