Engineering unique node boards per game seems like a waste of money to me.... yeah you save 15 cents worth of bulk components per board if a game doesn't need those particular drivers but between the electrical engineering and software changes to support that it's like they are spending a dollar to save a penny.... plus pissing everyone off in the process.
I think more likely the reason were seeing different node boards per game is that it was a half-baked system to start with and these things are basically mass produced prototypes with each release getting whatever the latest revision is at the time.
Stern could still down the road release a universal node board and make it backwards compatible through a software update. It's not like these things are controlling anything unique per game... it's all just switches, lights and coils... and sometimes a motor.
I know, wishful thinking. More likely someone else out there will figure out a way and make a killing once stern drops support.