An example of a longer bracket is the one on the canti brake post on my rando bike, the red bike pictured above.

That longer bracket, mounted on the bridge of my fork would be ideal. I’ll get one ordered shortly.

There's also a U-shaped bracket that goes under the V-brake wire and up that could work.

Here is a neat example: Aftermarket Dynamo Lights: a Clean Look

I have internal routing on my current bike, previous bikes have used a front rack and fenders to hide the wires along the way!

Dunno, I just used black plastic truck air line for the rear light wire. Comes in a bunch of diameters. The smallest one looks about the same as brake or gear outer, so it runs alongside those in the same mounts. Mostly because I have to fully demolish the bike when I pack it for travel, so the cover stops the wire from getting damaged when I jamb stuff in the box. Could probably do the same for the front, zip tied on.

Came looking for advice, left with the reassurance that comes with realizing that your plan isn't any jankier than anybody else's setup. I mount my light on the front of a porteur rack, so the cable has lots of area where it's just supported by air. Thinking that in those sections I might try enclosing the rear light and dynamo output wires together in heat-shrink with a 1/32" piece of TIG rod so that there's some support.

My usual excuse for messy dyno wiring is that the wiring on my bike is temporary. OTOH, some of my temporary wiring has been on a bike for 10 years. Once I get my travel bike painted I may actually try to do a permanent wiring job. I have provisions for most wires to travel in the frame/fork.

I prefer to think of my dyno wiring as a theft deterrent. Would you want to be caught riding a bike like mine, with the wires wrapped around the fork and everything?