putting a fueling station into orbit
something that a "super-heavy" might be really good for...
if travelling to Mars or the moon becomes more common, it's a fair bet that ships (yes ships) would want to refuel in low earth orbit, and how do you get the fuel "up there"? With super-heavy boosters!
Also components for building a REAL space station, like the one we see in the 2001 movie, would requier "super heavy" boosters.
Note I'm suggesting a Falcon Super-Heavy here because 70 tons is kinda small when it comes to things like fuel and water+supplies for space hotels and interplanetary travel.
Q: how many additional boosters can you strap onto a Falcon Heavy before it can't handle the load?
A: let's find out! [but first, get the Heavy off of the ground, and launch something more useful than a car]