There are various documents about in different countries addressing the regulatory worries. At the end of the day, it comes down to risk assessment and risk control.
The historical failure rates can be determined and, a bit like ETOPS, the aim will be to achieve the sort of rates acceptable on existing operations.
So far as the concern about what do we do if the only one stops, operational restrictions can be developed to provide a reasonable chance of a successful forced landing .. things like minimum cloudbase and below base visibility, maximimum distance from a suitable forced landing aerodrome considering operating heights, specific crew training programs etc etc
Nothing is perfect in this world .. all we can do is try to control the risks our way. Given the commercial pressures, it is likely to be only a matter of time, education, and development of sensible controls before SE commercial ops are an accepted thing.