Not sure on the weight, maybe 8-10 pounds. Most of this stuff is pretty small, my total volume here is less than a cubic foot and it's hanging about my navel. Keep in mind that BOB is extra gear, this is the critical stuff. BOB holds more food, more water, more FAK, more shelter, more socks, better knife, better light....
There is a Vic Hiker in the core kit, along with a glasses repair kit. I EDC a LM Supertool, pocket knife (varies some), Micra (key ring), Squirt E4 (bag of tricks) and Vic Camper (bag of tricks); BOB has a spare Ka-bar attached to him. Not worried about sharps.
The drop cloth is bulky and somewhat fragile, that's why I want to replace it with a slightly smaller tyvek. I had one of these that I cut down, but it wouldn't repack properly and ended up taking more room than it did before I cut it down. Machine rolled vs hand rolled.
The redundancy on fire starting gear is the result of repeated hypothermia and frost bite. I don't fear the cold, but sure as the sun rises I respect it, the same way I do a catamount. And I don't trust my skills at building a fire with a bow drill, not at 30 below. I'd rather have it in the kit that I don't even have to take off to get into- personal preference.
And the esbit is there becuase building a fire, while easy, can also be a pain in the butt. I'm afraid part of my "STOP" list includes making tea in one of the two halves of the mess kit that the core kit lives in. If sitting down, thinking, and looking around while the tea brews gets me unstuck in ten minutes, I'd rather not have to spend time being 110% positive that a fire is out. Also keep in mind my situation- rural roads. I honestly don't want to leave much of a trail unless I choose to.
And I agree about the buttpack. But they don't work as well with a full pack, but a chest rig does. Having tried to jury rig the old carrier for my ditch kit into a chest rig for many years I eventually gave up and bought something made to work the way I wanted it. And this thing breaths wonderfully, better than any vest I've ever worn even though it has all the practical space of a modular vest, due to the lack of a back.