Issues
Sultan,
The lateral load issue is resolved through the use of a spreader bar.
The engine failure case is resolved via linking the hook release systems. The old fashioned way thru wiring through the spreader bar or nowadays, thru a radio link.
Another technology that has been flown is a Load Stabilization routine within the AFCS or FBW system-that would be an asset for a future twin lift project. Funded by the Army and flown quite successfully on a CH-54. Being Army funded, that technology was handed to Boeing for their HLH design.
Remains to be seen if potential users can identify enough loads to justify the design/qualification expense.