Feasibility- Flex Capacitive Touchpad
Yes, a flexible PCB (FPC) can work.  Make sure the circuit is secured such that it doesn't flex or move in system.  If it is going to flex in-system, make sure you understand exactly what you need from the touchpad. For example, it will be a lot easier to design a system that only supports 2-finger multitouch for gestures compared to a system that requires resolution of 10 fingers.  It will be incredibly difficult to get a flexible, 10-finger, touchpad working.  I would not  attempt this unless that is what you plan on spending the next two years doing.

If you can get away with a two-finger solution, Cypress has the best solution for you.