My idea for a solution and possibilty
Okay, lets say the current MB is not able to sense 3 fingers. But it is possible to make the trackpad to recognize 2 finger swapping and 2 finger scrolling.
What I meant is, when the user swips with his/her 2 fingers horizontally, the software detects the movement and recognize it as swapping with 3 fingers as in MBA.
When you swip vertically, it means you are scrolling.
Because most of the finger movement revolves around 2 fingers, Im pretty sure some genius would be able to make a software to recognize your finger movement and make it understandable to a Mac.