Suggestion time! Allow for placement of backpacks in minecarts as a way of transporting them. Breaking the minecart would drop all of the backpack items akin to breaking a backpack block without sneaking. To equip a minecart backpack you would sneak + right-click it out of the cart. The backpack inventory would be accessible upon right-clicking it. To place a backpack in a minecart you would either sneak + right-click with an empty hand to unequip a worn backpack and place it in the cart, or you would right-click an unequipped backpack item into the cart.

That's fine! I would contribute it myself, but I have never touched minecart code and barely know anything about entities, so it would take me a considerable amount of time to learn the ins and outs of this feature. Maybe I'll take a look in the next few weeks.

Probably won't find time to do it any time soon, sorry.