I always see splitting before the ESCs, why not split after the ESC?
If you need a 20A ESC to power one motor, could you split the power coming out of a 50A ESC into two and connect a motor to each? I'm not sure about the weight/cost of a bigger ESC compared to two smaller ones.
I'm new to the hobby, so I am only guessing that this would work. The motors do not send feedback back to the ESC, so I really can't see why this wouldn't work as long as the ESC is rated at least the total current draw of both motors.