You're quite right about 'bums on seats'. A 10 hour Canary rotation carries 300 pax. 6 times AMS carries 900 pax. A double PMI carries 600 etc. The Canaries would need to be at least 5 times per week to fit the ej model. Half the flights would be half full/empty. It would only work as twice a week, and even then the prices/profit would not be attractive. It would be cheaper for the pax to take a charter package that organise it independantly.
The red-eye idea has been tried; fly the a/c when the airfields are closed. It is a killer for crews and removes the maintenance down time needed. Many airlines have tried this as a cash-flow' solution. The lack of maintenmace killed them off anyway. It might work with a larger a/c, but the business plan is fraught with danger.