I have one, and have used it several times. My main issue with the brew bucket is that you can't see where your trub line is (not that you can in a conical either), so you don't know where to position your racking arm to avoid it. However, after a few rackings, I've noticed that if you point your racking arm down as far as it will go, and rack until the beer clears, it'll create a nice little divot in the trub. Then the rest of your beer comes out nice and clear (make sure to cold crash for a few days to compact the trub).
Even if you extended the legs somehow, I really don't think there's enough space to put a bottom dump valve on the bucket. One, the bottom ends in a sharp point, so any valve off the exact bottom wouldn't be possible, and if you raised it a little, you'd be roughly at the racking arm valve level anyway.
Are you looking to harvest yeast with the bottom valve? You could always do this after racking by swirling and dumping into mason jars. If you're looking to "secondary" in the bucket by removing the trub, a lot of people will tell you that's not really necessary, especially with a conical bottom where the contact area with the yeast cake is minimized, and even more so if you keg, where your keg can effectively act as a secondary fermenter.
