I think it'd be a cool proof of concept, if nothing else.

Who says an EM game needs to be a flat playfield with few features? And who says a multilayered game with lots of ramps needs to have complex rules?

Make a cool game with ramps or multiple levels that has a rule set that fits within the confines of what can be done electromechanically.

It'd be expensive as hell, since you'd be farming for parts out of older games.

I think it'd be really tough to price out something like that. What was the BOM (adjusted for inflation) for a bally bingo back in the day? I imagine that the amount of electromechanical hardware would be the same between a "modern" EM game loaded with features and a Bingo.

I think, honestly, farming for parts would be rather inexpensive, since you'd just grab relays and steppers out from games in terrible shape (or incomplete, or whatever), but instead the high costs would be for designing the playfield, it's ramps, and it's toys--assuming the playfield is being meant to look like a modern game.