For more half-baked ideas, see my ideas tag.
RPM has some nice features for easily rebuilding packages. You can, for example, easily structure a source tarball so that an end user can build RPMs from it in a single step, and you can also easily rebuild an RPM from a source RPM. (See my recent notes on how to do all that here).
However for a lot of end users even these simple commands are too complex. And applying a patch to an RPM is beyond even that stage.
Here’s the idea: it’s a “try this patch” graphical tool. It takes a patch from a pastebin or email, and tries to apply it to an installed package. It downloads the source, attempts to apply the patch, rebuilds a new binary RPM, and installs it. (Of course it may not be possible to apply the patch, in which case it should either give the user a very simple message about what went wrong, or help more advanced users to manually fix rejects).
With this tool I could in confidence ask a user: “try this patch and tell me if it works”.
All the user has to do is to drag the patch file into the “try this patch” tool, and it will do the rest. If the patch doesn’t fix the problem, the tool lets the user “yum downgrade” to the previous version.
See also: A “view source” button for Fedora