Trying to avoid your visa run by just passing immigration is inviting trouble you don't want to have.

Work your plans out ahead of time and enjoy a day of vacation in somewhere nice!

From your question I read that you are living permanently in China, i.e. that you have a long-term rent contract there and probably also some type of work (promotion, teaching English, the usual suspects...). This at least used to be standard practice and tolerated by the officials, but rules/attitudes have changed recently. So while the visa runs you are doing used to be a part of popular culture, they are maybe not so advisable anymore.
This just as an intro as to why you might want to avoid additional scrutiny by the officials.

Because additional scrutiny (and plenty of it) is what you will get when you attempt this hack. As you state you have to fill in a yellow arrival card every time you do a visa run, and there you have to put down the vessel number you arrived with. I know that the immigration officials have a system in place that checks flight bookings (for the 72h visa-free transit) against names and they could have no problem checking if you arrived on the vessel you did claim, maybe even in real time while you are at the immigration desk. And there is where you get into trouble, as you have never really left the country, you are effectively overstaying and violating the terms of your visa. That is a bad thing. Next time you have any official business with immigration (and you have frequently as you have to do the visa runs), you will be anxious if they have found out and taken consequences. Avoid all of this trouble by going somewhere nice, or do the quick Jinmen, HK or Mongolia runs mentioned above if need be.

And one more practical issue: from as far as I can recall airside arrivals and departures are separated at least in PVG, so you might have extra scrutiny already when trying to get out of the airport again.