If I wanted to build a one-hander and didn't want to do it precisely
as described at chordite.com (using the middle and distal phalanges),
I'd put the two switches together so either or both could be pressed
with the finger tip. If the switches were the type with little levers
(as shown at chordite.com) this would be a matter of reversing the
outside one so that the levers were tip to tip.

I'd build the rest of the keyboard as described, just reverse the
outside switch and move the inside one closer to it (the outside one).
Then my finger tip could press either or both.

IANAL but I think that can't be patented because somebody (IBM?)
patented the idea of two adjacent keys simultaneously pressed with one
finger tip on their shared edge a long time ago and now it's free for
all because the patent expired. And it might be easier to manufacture.

Of course I think most people will find the result harder to use than
my keyboard but I don't honestly know that. It needs a trial. I
wish someone _would_ manufacture it.