Use Shift-right click on an armor stand to swap your armor to the stand, when wearing a backpack. The backpack, and all of it's contents, gets put on the armor stand.

Maybe that's ok. The contents aren't accessible. But it is a new way to store items. Honestly, in some ways I like it, but it may be a little OP. It makes it easy to create specialized gear packs for different tasks and swap them out when needed. Worth having a discussion about though, given the design of the backpack feature.