Back in the days before the internet became a distribution platform, there actually used to be software distributors that acted like this, they would publish in

Back in the days before the internet became a distribution platform, there actually used to be software distributors that acted like this, they would publish in hobbyist magazines as well as send out their own catalogs. Some were better than others and would get the small shops they represented to collaborate to make complementary products work better together. In those days you could be a one person shop and just write the software. I don't know how one would recreate that model in todays realities.