It might bring you more business and as an added bonus you get to work on the tires in a better position than on the car. Use a good torque wrench if you do for sure. Or as a percaution use an air gun and go over each lug with a torque wrench for security. I say go for it, the extra comfort you'll get from working on the rims while on the table will compensate for the energy it takes to change the tire, and you will be increasing profits too. Most shops have a disclaimer now when it comes to rims and if I was you I'd get one too, "Not responsible for damage to rims" but say it nicer than that. Just say you are very careful, but sometimes rims are damaged and people aren't aware of it and sometimes minor scratching might happen. I don't know of any garages around here that accept responsibilty for rim damage, it is well known that the car owner takes a chance when dealing with tire removal for any reason.
The car detailing market is much more competetive now with shops offering more and more services, seperating yourself from the others by offering additional services can only be a good thing.