Nothing to add really to this idea!
World of Steampunk would be a lot like World of Tanks, but with tanks and war machines from the era of the First World War -- packed in a steampunk universe.
Steampunk gives developers a world of endless possibilities. Steampunk machines can have wheels but can also crouch around, or fly, or swim. A properly designed World of Steampunk could even connect the dots between World of Tanks, World of Warships, and World of Warplanes!
There are tons of ideas on how to implement levelling up machine and crew skills. To be honest, it would be very easy just to copy and paste ready-made ideas from World of Tanks.
Certainly, though, machines and old-world tanks would be 100 percent more bad-ass than World of Tanks. But that's just me ...