if the Revo had a switch to turn it off and could charge accessories, I would probably build up an SP dynamo front wheel.

Paul, you explained it well. The color on a lot of these dynamo lights is hot. I find it annoying and fatiguing when these lights are behind me.

I am not in love with the Fenix BT20 but it lasts a long time (full night) and provides a good throw. It meets my needs.

I am hopeful a Revo Mk2 comes along (it puts out a ton of light) remedying the two above fatal limitations.