What will be the minum requirements that you will like to have to accept them under the umbrella of the project? It will be great to share your tougths there so we may consider adding them as part of the Tryton rules.
The number of new modules added by external contributors ( non maintainers) cleary shows that the incentive is not working now. Mainly the point of contrib module is to reduce the effort to share a module while do not reducing the benefits, so more people can join the shared efforts.
That’s already the case because people are just implementing the solutions on their own when failing to contribute them to Tryton. And this is something that I expect to be fixed with contrib modules. Having a more flexible rules will allow more people to contribute and work together in a more generic solution that works for all. Once they are shared in a common space is the work of the contributors to make it comptabile between each others and improve them step by step.
Main problem now is that is nearly impossible to add a new module to Tryton core to anyone except B2CK. So everyone is just creating their modules on their own and not sharing efforts.
To host such projects we can just use a subgroup like you proposed: Move some repositories to subgroup
To be honest, my main interest is in a place to share modules which are not accepted as core modules. Which currently do not have any place. And this place should be tryton-contrib.