The thing that I love about that modification is it is all very doable. Like Pascal Janin's PI-1 X4 board for GTB sys1 that has an attract mode, skill shot etc. There are a lot of people capable of designing these systems. After all it is obsolete (not cutting edge) electronics. A bit more processing power, 2 channel DACs for stereo sound, new sound samples, etc.
http://www.flippp.fr/en/