That should work as well. How did you run it at the bottom? I didn't see an easy way to hide it to get it under the dash. Mine is on the passenger side so maybe it is different. I still have the problem of running the wire to the back for the rear camera so I will probably keep my same plan of running them under the curtain bag at the top of the A-pillar.
Well, this subject coming up got me inspired to just fix it. I've been waiting for a warmer day but 35F and drizzly was just going to have to be good enough. It took all of about 10 seconds to pop the A-pillar trim off. Another 5 to 10 minutes of re-routing wires and taking pictures and it is all done and back together.
This was where the wires originally had ended up when I just tucked them in under the A-pillar trim without removing it. You can see they run over the side curtain airbag. It could be argued that they wouldn't interfere with deployment, but it could also be argued that they might.
This pic shows where I had the gps antenna for the dash cam with the wire laying across the dash. I had three wires to work with including the front and rear cameras and the gps antenna.
After pic with the two camera wires now running behind the side curtain airbag and the gps antenna wire running along the existing car wiring harness down the A-pillar.
I turned the gps antenna 180 degrees and now the wire is completely hidden.
Accidentally clicked this picture but the strange angle shows how my front camera is located next to and slightly behind the Eyesight camera. The location works well but it might be a little annoying for someone riding in the passenger seat.
This is on my 2017 but should be pretty much identical to the 2018 and other Gen 5 Outbacks.