This is my first OP on Pinside, so go easy if I'm breaking any pinball laws here 
I have a nice little 4 machine collection, including a Wonka and Wizard of Oz. The nephews and friends gravitate to those, and typically they have no real pinball experience. If I play with them, it isn't fun for anyone to watch little Billy lose his ball after about 20 seconds, and then the evil uncle hogs the machine for 10 minutes when it is my turn. Sure, I could adjust the overall game difficulty level, but that means I play even longer. The best solution is for me to step back and not play.
So it occurred to me: for any modern pins it seems that it would be a relatively simple coding effort to have an optional difficulty setting per player. When you hit the start button, you could use the flippers to scroll through and select a different difficulty level for each player. You could disable or enable the feature within the setup menu (it would be "off" for me the vast majority of the time, but could be activated when the family is over, or disabled for operators on route, etc.). Seems that would be a nice feature for home use players with the little ones. I'm not talking about an extensive new ruleset, but just a way to have the ball save activated longer and possibly "deactivate" the outlanes so a new ball is returned if not drained in the middle. I know 99.999% of those reading this could care less about this feature for yourselves, but seems like it could help open up the hobby more to the young ones (or even maybe help pull in a spouse into the hobby, therefore resulting in more machines in your collection?!?).
If this has been done, what machines do this? (just occurred to me, god I sure hope Wonka and WOZ can't do this, otherwise I'll have to disappear in total shame)
