Don, you mentioned a recumbent above. That might be a good transition from what you're riding now.
It's extremely rare for me to see other cyclists on my rides, but one that I do see occasionally is a fellow on a two wheeled recumbent. I've visited with him several times. He prefers it to the three wheeled version as it's more "bike like' to him, but is more stable than a typical two wheeled bike.
This fellow rides an Sun EZ model like this:
Sun Recumbents ~ Sun EZ-1 Lite recumbent bike from the Bicycle Man
He has his customized with all sorts of lights, mirrors, even turn signals. He has a small 12 volt battery behind the seat.
When he's at a stop, his upper legs are roughly parallel to the top tube with both feet flat on the ground, and still reclined in the seat. Very comfortable according to him. He said he's not sure exactly what it would take to actually fall from his bike.
The first time I talked to him was around two years ago. He was 86 years old at time and rode about 1000 miles per year.
Best of luck with your recovery.