Where are you???? I know several "on site" technicians who are very flexible in their appointment times...
However these folks are much in demand and thus the best time for them may not be the best for you... But they will still try to work with you as much as possible.
Look not for a dealer, but a one or two person shop (or truck) as dealer's have "Business hours" and all sorts of rules.. Where as someone like Nastrom's RV in either Mi or FL (Depending on the time of year) .. Well that's Rachel, nobody else, and she can be a bit more flexible..
Though that said she has a problem finding TIME to return calls.