recreating obsolete hardware is far more expensive than simply adapting modern tech to do the same thing. I think filling MMR with reproductions of all the old boards would have skyrocketed the price. it definitely would have reduced the potential features they could have implemented such as the "2.0" version they have planned, and would have prevented them from making the game properly handle LEDs (integrating fade, brightness control, non-ghosting, non-strobing, etc) or any of the other new features they've added. plus the beaglebone setup allows them to use the same boardset for all their remakes.

Not a stupid question, but basically no. The audio is compressed on the original due to hardware limitations. The remake uses a beaglebone which is basically a tiny desktop computer.

On second thought, maybe. PPS has announced their intention to release "WPC 2.0", which will be an upgrade kit for existing WPC and WPC95 games, allowing stuff like expanded rules and features that were removed from the original design for time or budget reasons. Better sound could maybe be included, I don't know. So far they've mentioned Funhouse and I think CV as 2.0 kits as far as I know.

They aren't being made endlessly, unless you also consider every Stern pin to be made endlessly too.