I think having two connectors (one data + one power) is too confusing and boring for the beginners.
However, if it fits, having a second dedicated power connector for advance users, is a good idea. And as it would be for advance users only, we can use a less friendly (hopefully quite compact and hidden) connector. We could think of it as a hidden features.
Or as a bonus feature (following the same idea we had about replacing I2C by CAN for special users).