They can do that without bankruptcy if, and that is a big if, they can convince the unions that the only way to remain competitive in today's market is for the unions to agree to wage and benefits returns with a guarantee that if the companies profits increase to a certain level, the wages/benies package is restored. Either that or have the union members swap wages/benies for a commensurate amount of stock in the company. That way, both the company and the workers would be able to survive and benefit in our ultra-competitive world. Bankruptcy gives a stigma to a company that is difficult to overcome. I know many people who will not touch Chrysler products because of their financial difficulties and bailout in the 70s/80s. If GM and Ford can avoid bankruptcy, they might be able to avoid the taint to their corporate names due to that, and working with the unions instead of fighting them might be the better alternative. Of course, that is assuming that the unions will be reasonable, never a certainty, in negotiating with the car companies. Now might be a good time for union members to speak with their union representatives and forcibly remind them that part of a smaller pie is preferable to no pie at all.
"....Either that or have the union members swap wages/benies for a commensurate amount of stock in the company"
I just took it as a given that if it doesn't involve more bennies or less work that unions would not cooperate. I think that is a reasonable assumption.
United Airlines did your alternate suggestion - The employee stockholders will be effectively zeroed out before they emerge from bankruptcy. I think this serves as an example - Union labor will always bankrupt a company, so I am sure they won't accept equity in return for working harder - It works with most other americans, but apparently not union members.
I think a GM/Ford merger is in the cards, out of necessity - either before or after a bankruptcy......a merged company that operates with voided contracts, pension plans, and a dramatically smaller aggregate workforce might survive, and might even make a car that could be sold profitably. Granted, this may take a while as both companies have substantial non-north american assets that can/will be sold off to feed the dying union beast.