MegaBall is one of my favorite games. A true classic.
I don't think there's a need for a WHDLoad install for it. As long as you have a native screenmode available, it should work. Older versions were a little tricky, but v4 is very stable and well-written. I've never had any problems running it on any of my (68K) systems over the years.
I think the trend of ADFs is only going to increase in the coming years as emulation becomes the predominant system for classics. It's the archival format of choice for system-friendly disks. I've also noticed a number of games being released on ADF that are written for 1MB A500s, presumably for the retro/novelty factor (and one-click WinUAE setup). In targeting the retro audience, it's kind of like we're back to the bad old days when developers didn't makes games installable because they assumed no one had a hard drive!

Art imitates life.
Am I correct that early (1990s) UAE invented the ADF format? I do wonder why DMS wasn't chosen as the emulated disk image format way back then...