Are you talking about a a thru-hike? You didn't mention budget or bottom insulation, but if you're planning on an ability to go to ground I'll assume you've found some pads that work for you in your hammocks. I'm also going to assume you aren't planning on bringing hammocks AND a tent, rather you'd rely on shelters when you needed/wanted to go to ground.
I have a sense you'll need to weigh your priorities and compromise on at least one of the specifications you outlined. Roomy zip-togetherness probably won't come in under 2 pounds. If you find some please update the thread so the rest of us can get in on the deal. If it was me, and I was thru hiking, low weight and practicality would likely win out and I wouldn't make plans for comfortable zip-together capability. Shelters are busy enough during the thru-hiking months that you won't be getting busy in one at night because you'll have company pressed up against you on either side, and if it is late morning or the middle of the day and you don't have company who cares about being discrete in a bag. Loss of nighttime cuddling stinks, but it beats lugging a couple extra pounds day in and day out.
Something that might get you close is this: Big Agnes MysticSL
Pros: Pretty light, down, pad sleeve might help your pad behave in the hammock, barrel shape is roomier than a mummy and makes for a better double-bag than two mummy bags zipped together
Caveats: They are very expensive, they require a pad like most BA bags, you'd need one right and one left zipper to mate them, not sure about ability to unzip foot box, not sure how well regular/long would zip together
These aren't particularly practical, but they are funny: Alite Sexy Hotness Sleeping Bag
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