I don't think it is realistic to expect anyone to contribute a quality add-on back to the project and maintain it. All of us that work (or have worked) on the project do so because it contributes financially to us in other ways.
If someone was to create a commercially viable add-on, then I think the smart thing to do would be to contribute back a "community" version that captures the essence of the customizations needed for that niche, but reserves a lot of the value added that comes from being experienced in that field for a commercial version. The commercial version could also include support. -Al
