I'm having a hard time visualizing a situation where you need to be running all these different versions at the same time. It is some sort of test or demo rig where you want to compare many versions to each other?

If I were doing something like that, I'd still just run a lot of apaches on different ports. I'd write a simple script that generated the config files, so adding new ones for new versions would be simple. That would solve the scalability problem. You could do something cute like encode the version number in the port number (e.g port 1001 eq version 1.001). The script that generates the apache configs could also make a few HTML files with links to all your apaches.

If, on the other hand you're doing something production, I gotta wonder why you want all these different versions running...