My impression, though, is that that level of complexity is the rationale for PPAs in the first place. To get that level of being able to update things on the fly like that, you sort of have to do all of what's required.

Another alternative might be to create a very simple install file as part of your package, and then put it up on Github for others to use. If you sign up with a public account (anyone can download your stuff, but not contribute to the branch (I think)), it's free. Then people who want it can just clone the latest branch to their computers and run your installer to set it up the way you want. The installer probably doesn't need to be any more than a few lines of code just to put the files where they need to be and maybe check for a dependency or two if need be.

Me personally, for such a simple project (as you're describing it), I'd go the Github route for distribution.