Sorry, I don't understand what you mean about the highest peak. On the Ingles, the highest point is as you approach Bruma, and you will make the climb coming from either the Ferrol or the Coruna. It's about 450 meters which isn't even the highest peak in Galicia (O Cebreiro is about 1300 meters).
My concern would be that there isn't any sort of marked route from Miño or Betanzos (the two towns where you could most efficiently divert over) to A Coruña, so that could be a big challenge.
Take a look at the elevation maps out there to really get a feel for the elevation changes. I'm not sure if they are attached somewhere in here, but you can find them in Johnny Walker's guide.
www.gronze.com/camino-ingles is another good resource. Click on "ver perfil de la etapa" to drop down the elevation map for each stage.
Hope you find what works for you, it's really a beautiful walk! Buen Camino!