I was away from bitshares for a long time and I'm definitely not up to speed on all the discussions that got us here, but this feels a tiny bit like using a second hack to cover the issues created by a first hack.
Doesn't the global settlement operation seem like it's what should be fixed? rather than saying "oops, global settlement puts us in an incredibly awkward position so we better create a new operation to clean up that mess."
But anyway, maybe it's easier to add a new operation than fix the old one. In that case, I just have one concern with your proposal:
The way your proposal is worded makes it sound like a single account would have to buy the entire settlement pool. I would think about a slight variant instead:
Instead of requiring the settlement pool to be purchased all in one go, why not let multiple accounts "bid" for it? Anybody who wants to can say "I want X amount of settlement_funds, and I'll commit Y amount of additional_collateral and Z amount of additional_bitasset." Then when all the settlement funds have been accounted for and there is sufficient collateral committed, all the bidders' bids are filled and the bitasset is revived. I haven't thought through how exactly you'd split the funds between the bidders, but I suspect there's a natural way that will be obvious once someone sits down and plays with the math.
Also I'd let people cancel their bids if they want.
BTW, I pull-requested a couple typos in the github document.