Although the adding of pockets is new, the idea of having a backpack separated into different sections for different things seems...familiar...

I think the first time I ever saw something like that...was in Pokémon...way too long ago...

Try downloading "Combuctor." It allows you to search your bags, along with click buttons to filter by "Quest Items", "Weapons", and further filter each category by item type. "Green", "Blue", etc.

If tailors could sew pockets onto our backpack and just have it increase the amount of slots it has; id be happy

On the "accidentally deleting" issue, maybe they could make the backpack like a hearthstone. If you trash your hearthstone "by accident" you can pick up another from any innkeeper. Only one to a customer though (i.e. Unique). Make the backpack slot unbound so you can put anything in there, but in the event somebody trashes theirs, they can pick up a new one at any innkeeper for free (and of course, it would have no vendor value).

@dawnseven : a more foolproof method would be :

unallow the removal of the default backpack, except when you attempt to replace it with another bag.