I'd be satisfied with Brompton merely improving the ergonomics and rigidity of the bike, plus improving stock components such as brake levers. Which are very badly designed and un-ergonomic. There's a distinct lack of design in a lot of areas (despite the core design being 30 years old). The head tube/stem area needs improving with regards to flex. Also the upsweep of the M bar is needlessly extreme and the space available for grip/levers/shifters too small. Though that could largely be fixed with a brake lever redesign. The brake lever / M bar combination is somewhat absurd in design terms.