HK Open is at a venue that is used regularly for large events. You have to go outside downstairs to buy snacks, water, hotdogs. If you want better food, there is a shopping mall and food court 10minutes walk away. The main train hub into China is right next door. There are a lot of facilities in the as well.
Within the venue, there are toilets and ushers all around. You are allowed to bring drinks in. People do switch seats but no problem if you tell them that is your seat.
As a viewing experience, the old venue was actually better - the audience were really close to the action. I notice all the SS now have the audience some way back from the courts but the improvement is that lighting is more selectively applied to the courts.
China Open is at a new hall - the problems you describe are event management. For a new hall, takes time to sort out the logistics.