We originally set out to and provided an unbranded version of our Plugin dashboard where 3rd party authors could put forward their plugin to be included. This didn’t gain any traction, in part because the population of 3rd party plugin developers is very small indeed.
Third party Discourse plugin creation is pretty niche and third party providing plugins with good test coverage is very niche! 
A lot of the freelancers in this space have either joined Pavilion or CDCK (or, in time, both!)
So in the end we decide just to collapse our dashboard into our branded community site.