The clamp of the Brompton have a V shape , not U shape that provides an immunity against wear and tear, there is rigidity issue at all with the Brompton joints which isn't the case with several aluminum folding systems.
The first lack of rigidity of the Brompton comes from its very long stem and second from the frame tube.
The best option is a design with a one piece main frame like on the Birdy and Swift. The Birdy having the advantage of a much smaller folded size close to the folded size of the Brompton.
Then, indeed, 50m or more wide tires is a major advantage, the tire width limitation of the Brompton to 35-37mm is a drawback.
Te Birdy also accept 50mm wide tires.