It's not about feedback only, also clear tactile button separation, not registering touches.

Repurposable physical buttons - maybe.

The more expensive way is with them being transparent and having their own small displays or being above the matrix, and has some similarities with what you say, the less expensive way is like Sony controllers.

BTW, PSP Slim was the most usable pocket computer I've touched. Text input was slow, but compared to touchscreens - more comfortable.