> you can get any bike shop to swap the rear cassette to a larger one

That's less likely to happen with the vanmoof. They have a custom-made chain guard which is integrated into the bike, and would not fit larger cogs.

They also have an internal hub, not a typical cassette and derailleur setup, so modifying the drivetrain is a more involved affair.

I think most local bike shops would tell you to have vanmooof do it out of fear of voiding your warranty.