Brompton has spent a boatload of money on a computer-controlled custom robotic brazing rig, to minimize individual variation even between skilled brazers who were doing it by hand.

Now extrapolate that rig to include back-purging for titanium. The cost would be astronomical. There would have to be a huge demand for the company to even consider that kind of outlay.

Could it be done? Sure. Will it be done? Not likely.

Brompton goes to great length to insure their parts are well engineered and last a lifetime. They have a funky machine to magnetically measure each hinge clamp compared to a known standard; any clamp that looks off in the slightest is rejected, as it might be fine for a decade but then suddenly fail. You don't see the extensive testing they do on the finished product, but it's there.