so I just recently subscribed to MAINEPREPPER on youtube and he's been doing a series of videos about his BOB loadout.
like many of us, he has multiple loadouts for multiple levels of emergency. his "level 0" is just his EDC, "level 1" is what many of us would refer to as a "get-home-bag", just an ultralight minimalist BOB with only the essentials, and his "level 2" is his primary OH SHIT bag.
the specific thing that I found to be very interesting and clever is that he's left enough room in his primary BOB to fit the other kits inside. it's a very interesting take on the whole thing IMO. the only drawback that I can see is that his primary kit is REALLY HEAVY!
idunno, either way, I thought it was a pretty clever system.