Something else to consider. Utilities just aren't there to handle many modern stadium features. Example - Electrical systems. Modern stadiums are power hungry monsters and it is my understanding the current stadium simple can't handle much more. Not to mention the structured wiring systems that a modern stadium needs to have in place. San Francisco's park has over 1200 wireless access points, 100's of TV's and concession displays, security cameras, cell phone repeaters, POS systems, etc. True we aren't an NFL stadium but we definitely need major upgrades.
The stadium is nearly 50 years old and it becomes a very questionable endeavor to install all that upgraded utility on top of old and apparently unstable infrastructure.