Stern in 2000 tried the concept of linking games to other machines once before with their prototype 'Golden Cue'. Never eventuated.
Since then the only piece of innovation that is worthy of the title 'innovation'; Stewies Playfield from Family Guy.
It was novel, it was perfect for the theme, worked very well and well constructed. But again it is not a progression for others to follow, I thought it was different and innovative for that title alone.
A concept innovated by Bally Williams in 1997 with NBA Fastbreak.
The "Stewie's Playfield" concept was worth following up. I'm sure Gottlieb thought it was a good idea on Haunted House.