Well ... who knows for sure what will work until it is running.
I decided to try the wet crank approach first and see how it goes. There isn't a lot of room in the case for oil except between the counterweights, but that's where the rod journal is anyway. I expect it to splash into the oil, throwing some up under the piston and lubing the wrist pin bearings.
I cut a piece out of an old clutch cover for a plate and capped off the intake port. Also drilled a 1/8" hole in the oil fill plug to relieve crankcase pressure. I don't expect oil to splash out because the fill plug is directly over the left counterweight which should be running smooth and not flinging oil. We'll see.
There is that narrow gap where the piston usually sucks in air from the intake/crankcase on the back side of the cylinder. I assume some oil will find it's way into the cylinder there. That could be good, actually.
As for the suggestion of running steam oil - I thought about that, but with a wet crank, I don't think I'll need it. Normal steam engines don't have closed crankcases. There's no reason for it. Oil cups or zerts are on the bearing castings. Of course, in this situation, I'm converting a 2-stroke motor, so I need to adapt to the situation. I plan to run just enough oil to cover the crank bearings.
As far as research into this, I've looked far and wide. There are examples of converted 2-strokes (see Youtube) used as steam engines, but most are actually running off compressed air and those that run steam are "experimental" and nothing is said about oil for the crank. The mechanism that operates the inlet of steam is called a "slam valve". I used a valve tappet sitting on top of the piston as an actuator. I like the flat broad surface of the tappet face on the piston. Other slam valve motors I've seen just run a rod on top of the piston. It appears to me this would eventually tap a nice hole into the piston. The other end of the tappet goes through the brass pipe in the head and into the bottom of a reversed ball check valve. When the piston comes up, the check valve ball is pushed up and steam enters, pushing the piston down. The steam is exhausted at the bottom of the stroke like exhaust gas from a 2-stroke and the cycle repeats. I've seen motors with this same design running right along in Youtube clips, so it should work. With 100psi of steam, there should be plenty of power. I don't know how well that power will translate to the rear wheel, but if it's enough to make the bike putt along I'll be more than happy.