To me there is no reason to implement the game logic using relays and switches. You can accomplish vastly more with a $2 CPU. What I appreciate is the charm and purity of the era. Here's my pitch!
A cabinet with an LCD display and translite. Probably has a knocker and chime box as well. All boards part of the base cabinet. Games are bought as playfields that you drop into the cabinet. Focus is on playfield artwork, layout, fun. Typically unlicensed themes. Open source allows the community to extend and enrich the game.
This would be a platform that encouraged indie games. The focus would not be on expensive assets like video and music but on innovative layout and game play. That is one thing I love about (especially earlier) EMs, the variety of layouts, flipper arrangements. Solid state logic provides the freedom to implement interesting rules and logic that we could not achieve in old EMs that were limited by how many relays and units could be fit into the machine.
Of course the question comes down to how much would it cost.....