I’m al for Berlin style and more depth in the OS, but agree with the complexity issues.
Having said that, a global edit mode for pages sounds fine to me.
I think the SEL(lock) button could come in handy for the extra modes in PAGE keeping the basic functions as they are now by making the "Berlin" stuff (which i really like) active by holding the SEL button when hitting EDIT.
The same could be said for different switching modes in GRID (instant or on 1st beat) Holding SEL(lock) while hitting one of the bank SEL buttons could toggle the "instant" switching modes instead of classic.
This way the basic functionality stays the sane, and the extra features come at the price of button combos.