1.) There is. When you remove soundstages down in the lower lot, or sacrifice the current Tram Plaza (Load/Unload/Repair Bay) and some of the Citywalk.
2.) While its true, Potter is a Juggernaut in terms of sales, and is continuing to gain massive amounts of profit to UC, Comcast, WB and J.K. Rowling
3.) If Diagons heading to the lower Lot, you can make it work. It just depends if they want to plus the experience in the trains and the layout itself of the track
4.) I'll disagree, wholeheartingly. Diagon Alley is home to some of the most iconic locals from the Potter Series, including Knockturn Alley, Gringotts, and the original location of Ollivanders. And not to mention London itself, which has been iconic in the series from many different locals in the film series; one notably is Kings Cross and then other locals like The Leaky Cauldron and also Grummalds. Also not even mentioning the Knight Bus as appeared in Askaban.