Making judo/jjj throws work

[Furinkazan]

I've trained at a BJJ school that teaches throws.  When rolling, we would ask our partners if they would like to start standing (i.e., going for a takedown) or already on the ground.

Problem is that the throws are modified for BJJ.  For example, with the ippon seoi nage, as you turn away from your opponent, you go down to your knees and pull him down onto you to load him.  I imagine that the execution is probably a lot more likely to fail than a standing ippon seoi nage, since with standing, you can use your leg muscles to assist with the throw but you give that up when going down on your knees - which means that in the BJJ modified version, you probably have to be more swift in the execution.  Any hesitation, and your opponent is stuck on your back.

There's also the fact that going down to your knees when executing a throw, although perfectly fine on the mat, is a horrible idea in a real fight.