I guess this could work in a way that upon tilting the camera downwards the quick-access-bar blends in from below which might be a nice feature with a touch to realism in a way that you see your toolbelt when looking down.
of course testing would have to show, as with most gameplay elements, whether something like this fits or just gets in the way e.g. when crouching while trying to hide from dangerous animals etc. so it feels disconnected in terms that controlling and accessibility do not match, thus the player failing in meeting his intentions because it might be possible that he wants to access his toolbelt in a situation in which he crouches or he does not.
also the toolbelt would have to show up when opening the rucksack anyway because that's where you assign stuff to the toolbelt.
accessing the rucksack would then have to be bound to looking over your shoulder because you carry your rucksack on your back and not on your front but I think if the inventory screen opened every time you tried to look around yourself to see some of the environment then soon players would start throwing their monitors through their rooms.
having said that, looking down to blend in the toolbelt might or might not work but I'd still prefer having to press a button to open the inventory instead of buying new computer hardware again