It would be useful to provide some background on how this is different from http basic authentication. I had a look a couple of days ago and I noticed that you are modifying the .htpasswd files.

Whatever approach we come up with should not cause headaches to non-Linux users.

Our modification is based on http basic authentificaton, and it's useless without it, BUT we provide solution what allow administrator don't worry about .htpasswd files then he wants to create/modify/remove user. Modifications, what must be performed in .htpasswd file executes automatically. No double work more! All users authorization information stored in database now syncronized with this files. This is the main purpose of our solution.