I have sometimes been tempted to buy a velogical.

One issue with removable dynamos is the lights still need wires. I used to use a dyno/headlight combo. Those were the bad old days of lights, but it did get me to work and back.

At some point, dynos saturate. I don't know what happens to drag at that point. I know SoN made a different dyno for small wheeled bikes, but it was pretty popular with people who used 700c bikes and I think they may have removed the distinction.