nice list! I've got a Pilot Custom 912 with a falcon nib, it's a nice pen....but if you're looking for flex, go bold and go vintage.
if you like the Diamine blue/black, check out Birmingham pen co's line of inks--some really cool blue/black variants.
I just picked up another grail, Pelikan M800 with a vintage flex nib on it. Now I gotta think of a new one to add to the list. Maybe a Waterman 58.