Or an electric dumbwaiter??

The other issue with turning the International Restaurant back into a full-service facility is that they'd need to update the furnishings. Even though retro is in these days, it would probably still seem too outdated for many. It seems like it was a very nice restaurant back in the day, as they even had a place for storing wine bottles.

All I need is a bottle filled with wine or two.

Sounds like a dining room logistics nightmare. A ticket is printed in the kitchen (on the ground). Cooks make the food. The food is then either carried up 50 feet (5-10 minute walk?) or up an elevator (2-3 minutes). Then its put under a warming light till someone is capable of taking the food to the table. If something is wrong/etc then well thats a nightmare. Not to mention drinks. 6-10 minutes just for a drink to return (under a no wait situation).

I don't think a 50-foot platform restaurant is realistic, but not entirely for your listed reasons. Specifically your times - those seem extremely exaggerated. And regarding the bolded part, I don't think it'd be hard to connect a soda fountain from the Tower Drinks area to the platform, enabling servers to refill beverages at the 50-foot level.

But once again, the idea is unrealistic for other reasons (location of kitchen, ADA compliance, etc.)