Gimp User Filter is a work-alike to Adobe's Filter Factory. It is a generic image processing plug-in that can be used to create new filters for The GIMP without having to go through the process of learning about The GIMP's SDK. Many freely available filters that have been created for Filter Factory can also be used with this plug-in.
If it weren't for the DAU...
... it would be for the money that this plan fails. Users can be trained to realize the necessity of proper sysadmin of their systems, but they won't like to pay for it unless - you bundle it with something else.
I would go for the homes themselves instead of the computers in them and sell the Internet connectivity via a medium-sized server in the basement. This server would sit between two firewalls, one of them connected to the Internet and the other hiding the end-users' machines from each other. Every appartment could then have a static (private) IP with no cross-over routing to other appartments unless requested by the users. The users can "administer" their machines as they did before (install their favourity viruses, trojans etc) but still have a (basically) secure connection to the net. The servers of this house will also provide them with e-mail and webspace and the users will have a rather good base level of security.
Of course, they still live on a risk with their self-"administered" boxes, but you can't sell them support for that, too -- it is just much too expensive for the users to pay for the mistakes they make.