New Idea for a fixed infinite speed hub gear

I don't think there's a need for frequent cable adjustment, and changing gear under load shouldn't be a problem (unless you pedal while changing gear).

Ibinscobled.

All cables stretch with use. So on any indexed gear system they need to be adjusted periodically. The Nexus keeps the cable under considerable tension, meaning more stretch, and more frequent adjustment.

Changing gear under load means changing gear while pedalling.

Typical scenario where the Nexus 7 speed really sucks is going up a hill, it gets steeper or you get knackered, so you want to change down a gear. The Nexus will stick you into top gear when you shift out of one gear, and refuse to let you into the lower gear
until you slack off. And slacking off is the last thing you want to do as it loses too much momentum.