The numidium shuts down in the 5th era, if the dwemer could actually return they could advance TES society tenfold I'm sure.
Bringing about by my speculation an 18th century romanised steampunk empire of sorts, perhaps expanding into Akavir territories?
Now a game exploring on the concept of two alien cultures meeting together in war or colonisation would be very intriguing.
Especially if it resembles early encounters between the British Empire and that of the Manchu Qing Empire.
If Bethesda could do this with an Empire of Tamriel and an asian resembling Akaviri dynasty of sorts, all the more relatable and better.
Put one side holding traditions at it's core (akaviri/don't use guns) and the other which likes to embrace new ideas (tamriellic empire/use guns).
Then that'd make everyone happy- as you could fight for one side or the other or even have different gameplay experiences.
But maybe I'm being a little too ambitious here, better to start small and work your way up like they say. So... who wants crossbows back?