The solution is to have the government take over their liabilities, while their bondholders keep the assets?
Yes that doesn't seem right. About the best thing for the taxpayer-voters the government could do would be to asset-strip the Big Three and any value extracted put into the public purse.
I think this article (if you read page 2) points to the obvious solution - government says to the big 3, declare bankruptcy, then we'll give you (or help you get) credit to avoid liquidation.