Actually, I've just come across another idea that I think I'll try incorporating soon.

If I'm using 2 sets... but I'm keeping the right-side the same on both... that means the only "different buttons" are on the left-side.
That is, if I only have the left-side different... you can do the same thing using just set 1, and using the L2+R2 combined set for the extra buttons.

This way there's no set-swapping. Just Set 1 and the L2+R2 "pop-up" set.

Not sure if it's easier or not, but I think I'll give it a try and see.
I may be too set-in-my-ways for now, though