I once had a client that asked if I could put wheels on all the patio furniture pieces she was interested in. This was an older lady that wanted to move the patio furniture around her deck based on the season. She could not lift the heavy pieces so putting wheels on them really made sense. The customer also wanted a hole drilled in the patio tables to put an umbrella. I have had several requests for the umbrella whole but not the wheels.
I was also interested in this question so I contacted the deck furniture manufacturer and they indicated that they could put the wheels on. There would be a fee however ( $30 per piece ). Most of the big stores ( certainly all the larger manufacturers, chain stores etc ) would never accommodate this type of request. This is a good argument that purchasing outdoor deck furniture from a smaller manufacture has its’ benefits.