You would need a mechanism for ordering. You need to order to go packing, condiment packaging, have staff at the restaurants now working on packaging to go orders vs in house orders. Then you need staff doing the actual deliveries of the food, and you will have increased room service/cleaning costs to take care of the clean up, either in the rooms, or the hallways now full of have eaten trays of food/stuff. Then multiply that through all the deluxe resorts
Now would it be a huge expenditure, based on the total budget for WDW resort hotels? I can't really say. Would it be a positive return on the investment to do it...personal opinion i don't think it would.