Ok then let me throw this idea out instead.
We should write a MonoGame modeling app.
That outputs its data to a existing format that is either open, non proprietary or simply a newer one, a heavily documented one, or pick one that seems to be the most stable.
I mean if you can load a fbx or any other format saving it again is trivial if you edit and then resave that data you essentially are modeling it. If you click a button to edit that data move it around visually ect.... you have what all modeling apps are just like blender or any of the others. Basically a viewer is the first step to a modelling app anyways.
What better api to use to build a modeling app, then the same one that will use the models for games based on it.
If nothing else maybe its a idea for the future as a modeller attracts lots of people including artists. So this is also idea that benifits the status of monogame itself and would make it more visible.