Almost all Pinball powerboards/rectifier boards use smoothing caps....Not sure how you've missed that in your research.

On modern games, 50V coils are only used on flippers, slings, VUKs...Most other solenoids that are used for diverters, ramps, target resets, etc. are low voltage....23V usually. And for the flippers, high voltage/low voltage combos are used so that the holding power is significantly reduced.

At 50V, a 200 ohm coil is only pulling .25amps. And with the ball traveling, rarely is more than a couple of coils on at a given time. Again, not sure why you think you're going to be drawing 10A in a short cycle. All coil actions are designed to be short cycle. Even when raising a ramp for example, the coil fires to lock the ramp up mechanically, but it doesn't stay energized. A separate coil then releases the lock and the ramp falls.

You can buy the early Bally flipper switch stacks...They have one normally open and one normally closed leaf switch on them, as the NC switch was used to bypass the low voltage windings (Bally coils were in series, not parallel like WMS coils), and the NO switch was used to drive an upper flipper on the same side. All microswitches also have a common, NO and NC connection....The NC side is often just used as a convenient termination point for the diode in standard pinball design, but you could just use the NC side for an EOS if you desired.

I'm a EE by trade and I'm impressed with your work. If you need to bounce any ideas off of me in regards to pinball electronics, feel free to shoot me a PM.

Depends on the coil configuration....Bally coils were in series (low and high) so the EOS opened up. WMS coils were in parallel, so the EOS closed.