Thinking about an electric recumbent build
 

I have one of the last Bionx systems installed on a road bike of mine. It is neat but overall I think electric systems are better suited to >2 wheel recumbents. That is because the weight of the battery system means that you still expend a considerable amount of energy just balancing the bicycle upright. That and the lowered efficiency overall.

So thoughts on how to go about this? I'm thinking a 2x1 trike (because I only have 1 bionx wheel) I guess with a rack over the rear wheel and maybe a cargo area for utility. Otherwise, there don't seem to be many recumbent manufacturers.

You have come to some interesting conclusions without any basis. A trike with a battery pack over the rear wheel is not a best practice. A battery location nearer to the center of gravity (under the seat) is much better. Works for two wheel recumbents just as well. The lower weight and complexity of a two wheel recumbent along with the aerodynamic advantages of the more sporting designs makes them ideal platforms for e-assist. We refer to trikes as either Deltas (one leading wheel) or Tadpole (two leading wheels). If by "2x1" you are referring to a Delta layout then, yes, there are relatively fewer of those around.

recumbents tend to be wicked fast because they have so little drag. I saw a crazy video years ago about someone in Germany doing something like 45km/hr on a low powered system.

45 kph is not all that difficult on a flat smooth road without elect assist. I've contemplated adding a motor to my ICE Sprint trike but my primary motivation is to help me handle the hills. I would opt for a torque sensing motor mounted at the crank. I'd probably mount the battery centrally behind the seat if I could figure out how to do it.