It’s now time for a group of Wall Street banks led by Morgan Stanley to step up. : Elon Musk’s shock proposal to proceed with his acquisition of Twitter Inc. for the original offer price poses a headache at the worst possible time for Wall Street banks already struggling to offload billions of dollars in buyout debt they committed to in better times. After months of legal drama in an attempt to back out of the deal, billionaire Musk is now willing to buy the social-media giant for $54.20 a share.