Wiring is just fine outside the frame...If it's well protected, sealed, and not cheap primary wiring.
As above, RNR makes a great frame. The axle on mine isn't simply drilled through the frame and rest on the axle perch. They used a bracket to mount to the side of the frame, therefore no holes in the frame, and the brackets provide additional strength.
But they need a basic example how to do wiring. I replaced all my wiring on my 2020 ARC 12.
1. Use marine tinned wire. Regular copper turns brown and then disolves in the salt.
2. Run the wiring in a automotive heater or fuel line hose.
3. Crimp, Solder, Seal, and fasten all wires. My ground wires are through bolted into the frame (coated with dialectric), not just a sheet metal screw.
4. All of my connections are a little unorthodox, but they work! I solder the connections, then put a household wirenut on it. Then fill the wirenut with silicone. Finally cover the connections with some gorilla tape. Electrical, chemical, mechanical, and vibration proof.
5. Invest in a quality coupler, a cold weather pre-molded connector lead, and a distribution box.
wiring here -->
BOAT Wire | Marine Grade Wire Products
Molded cable-->
https://www.etrailer.com/Trailer-Wiring/Bargman/54006-057.html
Coupler->
https://www.etrailer.com/Straight-Tongue-Trailer-Coupler/Demco/DM15000-52.html