looking at your images, i'd say:
you could either pick up and old p.o.s. ecBronica with waist level
finder
great for candid shots of people when you don't want them to know
otherwise,
the Pentax 6x7 is pretty awesome and you can always cut the top
centimeter off if you want to be a square.
A Blad is a lovely creature but I wouldn't go from an F100 and D100 to
a Blad, actually, the ecBronica might be a bit confusing too.
Anyway, shoot a heap of Velvia and have a blast, you can crop to your
hearts content.