When you have to lift your entire left hand away from WASD, a quickbar is no longer quick.
You were entirely right when you made your initial binding decisions and it's sad to see such a good break from convention get discarded because it hit a small conflict from a new feature- a conflict that ...

(First found and fell in love with Factorio back in mid-2015 and I am finally registering on the forums just to state my preference on this. I do trust that you'll come to the right decision without this post anyway, as I have been continually impressed with the rate and quality of art and design ...