I think this is a really great concept, @mathieubossaert, thanks for bringing it up. Not only are sample forms a great way to share knowledge, they're also really helpful for developers to build test cases from. The more real, complex forms we have access to, the more we can ensure that the tools meet users' needs.
I really enjoyed your blog post and I think that at the very least you should write a showcase post that links out to it.
I think that the Showcase is a good place for this kind of sharing and I agree with you that a more structured approach would help make things easier to find. I vaguely remember that @Xiphware had started putting together a template but I'm not sure what the conclusion there was. Maybe it's something that could be picked back up?
In terms of indexing, there's The showcase index which I had started in the hopes of making relevant examples easier to find. I haven't had the time to keep it up to date but it's a community post so perhaps others could start updating it and adding other dimensions to index on?