I thought that the POTJ Ben Kenobi was pretty good. And that only came out about 2+ years ago? It's one of my favorites from the POTJ line. There was also Ben from the 25th Anniversary 2-pack. That was definitely an upgrade from the POTF2 Flashback figure.
As for how they could improve it....
Make a similar figure to the POTJ version, but with softgoods from the waist down. Then, also give him the Jedi robes, also in softgoods. The one that came with the SAGA Obi-Wan pilot is pretty good, so that's a starting point.
Then, package him as a Deluxe figure with the Death Star's Tractor Beam control station. That would be a Ben Kenobi I'd be very pleased to see, and would be happy to buy.
And finally...give him his own lightsaber hilt. My one and only gripe with the POTJ Ben is that he had Luke's lightsaber hilt attached to his belt, not his own.