that would be an interesting...

The mechanic already exists, There already is wrapping paper in the game, and you can package your items (i remember a bug where gifts got the "of the ___" suffix that the item had)

All they would need to do is expand this mechanic to allow 2+ items to be put in the package.

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Main thread
I've taken my pack everywhere with me.... Its been messed up since the beginning... but its served me well.
Its waterproof, and if you are careful, you can store troll sweat in it. I've had it full of sewer carp before too (still haven't found the rat after 500+ carp)... best of all, you can fit an entire rotting bear carcass in it, even more depending on the stage of decay.

I don't think its necessary to have a bigger backpack...
That is what your bag slots are for...
you want a 24 slot backpack? why not just make bags with 2 more slots in them... you'll get the same number of slots. Blizz has been increasing the bag space consistently.

The only bummer is the lowbies... I find it impossible to meaningfully quest without buying my lowbie a full set of 16slotters at least. Its downright painful to lvl with no bagspace. If they did improve the default bag, they should not make it scale with level, they need to show some love to the lowbies who can't find room for the endless quest items they pick up...

But, on a similar note... any changes to bag space would totally mess up the Clamming Twink bracket... It was bad enough when they lowered mount requirements so clamming twinks could get from spawn to spawn faster. Then the Clammer QQ got it so you could open clams while mounted... and 22 slot bags weren't enough for them either... so they got clams to stack... They might as well just have a vendor that gives away free clams. talk about world of hello kittycraft.