One of the issues I could foresee with working the BL on a bar is you won't be able to get your lats and triceps connected. This would make the BL more difficult.
You just have to scale the supinated BL back down from the pronated BL. So if you were doing it a straight body pronated, you might have to go back to doing it in a tuck and so on just to let the elbows get used to it.
I think after you can do the BL straight, it may be a good time to take the triceps off the lats. You could train it that way from the getgo but I don't think any of my little guys would understand how to do it.