I don't know if you'll be coming back to read any more replies...
It depends on whether you are the developer trying to build/architect trying to design or a person trying to fight the construction of the stadium.
Some more references for you (if you don't already have them)
TERPS (FAA Order 8260.3)
http://www.faa.gov/about/office%5For...260.3_1-18.pdf
Airport Design (Advisory Circular 150/5300-13)
http://www.faa.gov/airports_airtraff...50_5300_13.pdf
and to keep reading on to the next paragraph of Part 77 - Part 77.25 which defines the imaginary airport surfaces and planes.
http://ecfr.gpoaccess.gov/cgi/t/text....3.1.3&idno=14
You might also want to get a copy of the airport's Obstruction Chart - it depicts the Part 77 Surfaces and all the obstructions which penetrate the airport's Part 77 surfaces. SJC's chart is available on paper only, but the FAA is slowing getting them electronic - an example
http://www.ngs.noaa.gov/AERO/Digital.../LBB_OC241.pdf
In the end, all the FAA can do is declare the proposed stadium a "hazard" or "not a hazard" to air navigation. They cannot stop or prohibit the construction of the proposed stadium if it will interfere with aircraft. So effectively there is no maximum height to that stadium. If the stadium does pose a hazard to aircraft, what the FAA will do is raise the approach minimums or displace runway thresholds to regain the obstruction clearances so that the stadium won't penetrate the imaginary surfaces or just cancel affected instrument approaches.
So no problem from the FAA if the stadium is a hazard, but you might have problems getting the building insured if the FAA declares the proposed stadium a hazard to air navigation.
With the proposed stadium so close to SJC (within 3 miles I think you said), what will happen is whenever there is an event going on at the stadium - you will effectively close the airport during any event at the stadium - commercial flights won't be affected, but no one else will be allowed in or out while the event is going on. Since SJC is probably a very busy business jet airport - it would disrupt things for them. An example would be Montgomery Field in San Diego during the Super Bowl a few years ago.
AOPA was successful in getting two floors lopped off a building that was getting built in San Diego that would have interfered with approaches into Montgomery. The original design was declared not a hazard by the FAA. Then the developer added two more floors which would have interfered with the appoaches to the runways. Since the FAA couldn't stop the developer from adding the two extra floors, AOPA took up the fight and I guess they won or came to some settlement.