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Perhaps you can replace the switch carrying PCB under the buttons with a panel of small pneumatic bulbs connected to differential pressure sensors, then feed the resulting signals to both your study instrumentation and the normal keyboard connection on the computer.
The simplest way to build such a panel would be to simply loop a short section of small silicon tubing onto the surface of the panel between two holes, similar to the way you would mount a wire jumper on a through hole PCB.
Using my backyard techniques I think I'd be looking at a scrap musical keyboard, even the cheap ones these days have touch sensitive keyboards, one of these modded might just do the trick, I've never messed with one but I'd spose that the resistance of the element would be dependant on how hard you shove.