welcome to geekhack!
First of all: anything is possible. Well maybe not anything but lots of stuff, for sure.
like lots of things, there are a few ways to get it done.
Firstly, such a keyboard is easily possible with a large touchpad and a controller (like the fingerworks touchstream) as well as lots and lots of clever programming.
You could also implement something like that on top of a normal cherry mx keyboard with some flat top keycaps and capacitive sensors, and a controller for it all. I recommend very thin magnet wire for the 2-3 capacitive wires between the keycap top and the controller, so as not to affect the switch tactility much.