A Steam console doing those things would be pretty awesome, but it also wouldn't be a "console" anymore. If it were also able to function as a general-purpose computer it'd be a PC gaming box essentially, fashioned like a console, and would cost more than a typical console because by it's nature of being open-platform would mean storefronts and such can't be locked down to those which only Valve own/have control over.
Plus, they'd eventually have to allow any Microsoft, Sony, Nintendo, Epic, CDP etc. storefronts/launchers on the platform anyway as regulatory bodies would deem it a general computing device. At which point with all of these factors, it wouldn't really be competing directly with the PlayStations or Nintendos of the world (though would still be competing with them for gaming time & dollars obviously).
Good point though in that it could cause contention for Microsoft if they popularize the concept before Microsoft does, hence why I've been saying if MS continue gaming-specialized hardware, it should be in this type of avenue, and adapting a business model fitting it. Plus both Windows and Surface need an infusion to boost them, as does Xbox hardware...why not just merge them together at this point?