Haha, most artists I work with tend to be fairly open about the concept of re-amping. A lot of them are coming to embrace it. They are tracking their guitars on a budget at home, using their PODs to monitor, then reamping come mix time. If re-amping isn't so big on their agenda, I usually namedrop a little (mesa, rectifier, triaxis, XXX, van halen, nevermore, sneap, 5150) and it does the trick.
I think if people involved in a project start working against each other, the working relationships suffer immensely. I would only resort to re-amping something for a band without telling them if they were being entirely unreasonable, and I thought that the product, as is, would be something I wouldn't want my name on. They always have the option to 'ok' the final product. Even if they aren't aware of the processes you've gone through to get to that final point, if they like the end result, what does it really matter? Having said that, practicing honesty is still an important part of not just the business, but maintaining human relationships in general, whether personal or working ones.