[...]...wouldn't city based demand largely fix this problem at those airports anyway...?
Honestly instead of doctoring on such minor things over and over and over and over the whole problem should be solved.
I have to think at House MD I watched yesterday: "If you wake up and your wallpaper starts to melt, your curtains are gone and the water in the toilet boils - which problem do you solve first? NONE OF THEM! Because your house is on fire!"
The game is stable at this very moment. It could be at this development point for weeks or month until city based demand is done. If city based demand is made like we all hope, there is no (real) slot shortage anymore in the future because people build their own airport and don't simply occupy real world airports.
I don't know a single person in this game who doesn't look forward to city based demand but nobody ever complained he can't fly to a single airport.
In fact I had the problem several times I wasn't able to fill out the routes to airports like Hong Kong or Heathrow or even Milano or JFK because they are sometimes short on slots. But funny thing is, my airline still survived.
At the moment I'm flying out of Heathrow for the first time in my AWS career and it's no fun. It's like a damn job to always wake up and check for new slots. If the number of slots is not only decreased by a further amount (30%!!), it also gives free slots to every random joe in the gameworld, I can't believe somebody who has left a little bit of brain anywhere in his house would HQ at such an airport.
So, long text short:
Please stop putting time in minor changes of symptoms of a problem. Please change the underlying problem and implement city based demand, even it needs (much) more coding time. :/