...From what I understand this could be advantageous over a leveling base since a ball head potentially has a wider range of angular adjustment over leveling bases. Except that the whole rig is taller due to the ball head.
Depending on what you're leveling, that tallness and wider range can be an advantage or disadvantage. Using a ball head as a leveling base by adding a panning clamp above (or using an Acratech GP head in panning mode) is great if you're balancing something light on top that doesn't need extreme precision.
For example, one panorama setup I do uses a lightweight Nodal Ninja R10 panorama head and a Sigma 8mm fisheye on a crop sensor camera. If leveling is half a degree off it's no big deal, and sticking this light rig on top of the ball head that's already on a tripod is quick, easy, and accurate enough.
Another pano setup is a Gigapan Epic Pro, a 15mm UWA on full-frame, the whole rig weighs about 11 lbs and is very top-heavy as well. Though you *could* level on a heavy ball head, it would be very awkward, and run the risk of catastrophic failure if you let it drop without the ball fully tightened.
Gravity. It's the law 
That's where the true leveling base, with controlled movement, is really needed. I could see the same needs when using a heavy lens on a gimbal head...
