Couple personal opinions..
1. I think it's a little big, but if it were me I'd only want one flathead bit (as you have) and just a couple phillips bits. If you stay at the size you have, try to fit in a little extension that you could stick in the middle of if it so you can grip the main tool body and use it to put more force on the binding insert screws.
2. The idea is really good with being able to get at them, I hate fumbling with tiny tools when I'm on the hill. Again I'm not sure of the material on it, but I like being able to grip stuff easily, and would be more inclined to buy it if it had a rubberized coating on the handles like some screwdrivers/tools have. Looks like you may be able to use this pretty easily with gloves on too which is a huge plus. Leo's idea of a little screw compartment is awesome. Possibly magnetic in case you drop something at a bad time?
Sorry for the information overload, trying to think of everything here.