What's the point? If your admittance is in significant doubt then you should be applying for a visa in advance. And if it's not, what's the point in having a system where you have to wait for the whole plane to pass through immigration before you're allowed to move on? There is are many good reasons why immigration is generally done on arrival. The few exceptions are where it tends to be a simple procedure either because of the number and nature of the passengers (CWLCY) or because of the two countries involved (e.g the Eurostar).

Barmy idea if you ask me. I just want an efficient procedure upon arrival. That's perfectly possibly with good management, however stringent the process is.