It is possible but not been done. The grand-stands would be tricky to make because they use guest animations. This means the seating would have to be exactly the same or your guests would look weird. Also it would require the ingame guest hack to be changed so they would even use it. Problem with that is there can only be one guest hack or it would cause problems (has done in the past). There is one currently available at DG and that would need to be updated by Jay if a grand-stand was made.