SJC, while super convenient (I live in the South Bay) isn't a premier airport and will never be. Half of it is old and needs remodeling.
We need housing and density so much more than we need more flights out of SJC.
Obviously we also have to require aircraft to take off to the north, yes?
Let's see how we can implement this proposal.
SJC has two parallel runways: 30L/12R and 30R/12L. The runways are 700 feet apart. [1] [2]
We could operate the airport like a two-way highway where you only drive on the right. We permanently close runways 30L and 12L, and allow takeoffs only on 30R and landings only on 12R. So you approach from the north and take off to the north.
This will result in oncoming traffic 700 feet to your left, whether you are taking off or landing.
Passengers may get used to seeing other jetliners zoom by them at 250-300 miles per hour. After all, we do something like that on the freeway every day.
As a pilot, my worry is the wingtip vortices, affectionately called "wake turbulence". These are little cyclones that come off the end of each wing, travel with the wind, and can flip you upside down! The two-way traffic will assure plenty of opportunities to get caught in one of these.
OTOH, the oncoming traffic and wingtip vortices may only be a problem on a very calm day.
On many typical days of the year with moderate winds from the north-northwest, we may have to close the airport for landings and only allow takeoffs. Conversely, when the winds reverse due to weather, we will only allow landings and cancel all takeoffs.
Perhaps this plan is not quite as simple as it first seemed.
[1] Runways are numbered by their approximate compass heading divided by ten. A runway can be used in either direction depending on wind conditions, so it has two different designations that differ by 18, or 180 degrees. When an airport has parallel runways, they get an L or R suffix for left or right. So runway 30L and 12R are the same physical strip, at an approximate compass direction of 300 degrees if you are approaching from the southeast, or 120 degrees when approaching from the northwest. Similarly, the parallel strip is runway 30R and 12L.
[2] SJC runway map: https://upload.wikimedia.org/wikipedia/commons/a/a6/SJC_Airp...
So you approach from the north and take off to the north.
I also mentioned that crushcrashcrush's plan would require closing the airport to "opposite direction" traffic on all but the calmest of days: you would have to allow only takeoffs in normal winds, and only landings when the wind reverses.
My comment was a tongue in cheek attempt to point out the problems with the plan by taking it seriously.
I did forget to mention one other issue: even if you required approaches from the north and takeoffs to the north, it still wouldn't allow you to build taller buildings south of the airport. Airplanes need to be able to go around (abort a landing and take off again if the approach isn't right), so in that case you would be taking off to the south.
Also, you approach based on the wind.
you can only approach SJC airport from the north, not the south
On one occasion, I flew via SFO. I vowed to never ever do that again. From that point forward, I always flew via SJC, and I was much, much happier. The airport was clean, reasonably up-to-date, and never had major traffic problems that I saw.
I would be very unhappy if that airport got shut down or crippled just because some people want to build tall buildings in the area.