Giant Bird is correct thinking this is abusing the spirit of ETOPS rules. The risk may be small, but the practice carries the potential for a massive corporate disaster.
There is no Gods of spirit when it comes to flight safety. It is fundamentally based on statistics from historical data..
Even when assuming there is an outlier earlier engine failure than expected, when you estimate a second engine going you are well within the average non-RR fleet probability of completing that sngle flight