it definitely would be OK. the pleco might miss having gravel to eat algae from, though, so make sure it still gets plenty of food. driftwood would be a good way to replace the lost surface area. they love it.
I have a sand bottom and a pleco, he/she does just fine has grown very quickly and seems to be very healthy. Although I may be trying to find a new home for him since I didn't research first and had no idea my little 1" pleco could grow more that 12"!!! He's around 6" now.