I think this issue is hugely personal preference. Try all sorts of setups, use the one that gives you the best balance and best range/freedom of motion.
Toe lift on the front foot does not decrease ROM if you do not increase boot forward lean, and if you do not ride front-foot-heavy. Some people ride way over the front foot, often aggressively leaning forward at the waist. For those people, yes, increasing toe lift would probably decrease ROM. I like to keep my body movements more between the bindings, and with a more upright torso. For me, toe lift on the front foot and heel lift on the back foot simply allows me to use a wider stance (19.75") for greater stability and balance with comfort and <i>increased</i> ROM. Riding flat definitely decreases my ROM at this width.
Some people argue that the bend of the board in the turn cancels the effect of flat bindings. While that is true in the turn, it is not true out of the turn, which is equally important.
We do not walk flat footed, we walk heel toe heel toe. Take one step forward and freeze when your front heel hits the ground - your rear heel will be off the ground.
Meh, like I said, big personal preference factor here. Experiment.
DarkClone - you don't want to drop your 10+ years around here. Many here have you by a factor of 2 or more. It doesn't matter.