Very interesting idea. Here is my $0.02. I would definitely consider it for a week at a time here and there through the season, but it would have to be absolutely safe(guaranteed/insured), convenient, and relatively inexpensive.

Downside to leaving it there.... 1) Can't use boat for local trips during week. 2) Worry about boat being vandalized. 3) Weekend plans are now less flexible, I know that I have to go back up and pick boat up.

Looking at the downside, I don't know how much I would be willing to spend. $20-30 per week? And from a business point of view, I don't think I would want the responsibility of storing boats for $20-30 per week.