i cant beleive what im reading here ,you talking about taking tops off and replacing with ply ,you cant do that
if the appliances arent going to fit back after tiling you should not tile it
let some other mug with them type of brains do it or offer the customer a suitable floor covering i.e. karndean or amtico its not that much dearer than tiles
i suppose the next answer will be ( but its marine ply )