Unfortunately, I'm far to be a "genius"...
And i'm agree, with the "cycle system", do not put more than 4 games.
with the pic, you can make an interesting thing (that i've already used in other systems like master system, megadrive(genesys), super nintendo...)
Use the reset line to switch games (and save the state in the pic memory).
When you power cycle, the games loaded will always be the same unless you make a reset. (run+select on pce/tg if i'm not wrong)
the pic cost is completely out of problem (less than 1$, what a joke) and 100% free if you use the microchip samples parts.
Maybe turbokon will use this kind of thing in a future version.
I'll stop writing here, i think i've already polluted his thread.
PS. yes for the flip flops, but as you stated it can not work alone, so a pic is more easy to integrate (8 pins, far more than 4 games).