Incidently, several manufacturers* offer a front hub motor to turn a regular Brompton into an e-bike.

If the original fork is strong enough to withstand a hub motor with a torque of about 50Nm, wouldn't it be able to also take the force from a disk brake?

If all it takes is finding a competent LBS to weld a disk caliper adapter on the right side to fit the Brompton's folding, getting the kind of 74mm wide hub I mentioned above, and building a wheel… it'd be a nice upgrade.

Of is the effort from a disk brake very different from a hub motor?

* AKM-F, Crystalyte NSM/SAW20, Swytch, MkXR, Q70, etc.