For a hybrid setup, regulations will likely require that both the conventional engine and the electrical system to be powerful enough on their own to still take off if the other system fails after V1.
Still, that's massive savings over the current twinjets, which require two engines, both powerful enough to take off after a failure of the other at V1.
Sounds reasonable. But in an unlikely best case scenario, the electric part might somehow be certified for single engine reliability, capable of everything except endurance. A wave of comparatively liberal cruise engine development might then catch up with a few decades of combustion engine refinement.
Still, that's massive savings over the current twinjets, which require two engines, both powerful enough to take off after a failure of the other at V1.