Is it possible to have only 2 cassettes large and small?

[cyril1]

I feel like the shifting could be difficult, but please let me know, thanks for advices
It would be for a Brompton C 2 speed, have 1 speed for hills, 1 for flat (I don't want their wheel hub because it's heavy, and not the 4 speeds customisations because it seems difficult to do)