You are an outlier for the types of folks using these plans and a good example of why there is no such thing as a one size fits all plan. We shoot for a middle of the road approach to these plans. All our plans use the same principles as are laid out in our book. So you can customize to your own needs by applying those principles to your own needs. Keep the main guiding principle for all aerobic base training in mind: YOU CAN NEVER HAVE TOO MUCH BASE when it comes to the aerobic support system. So, do exactly what you are suggesting. Add more Z1-2 work in the mountains. This should work well for your situation.
Thanks and good luck.