A few things I thought about during my run in regards to GZ- look at Daniels Running Formula, Canova, McMillan, Vigil.. ANY coach or program out there does not advocate what you are thinking is correct. Jack Daniels (considered an "intensity" advocate) even says to run easy for the first 6 weeks, then the last 8 weeks even has ZERO anaerobic work. His programs are 24 weeks long... so that's a total of just 10 weeks of speed work.. you're going to try what? 23 weeks of it (however long it is to Pikes Peak) plus what you have already been doing.
At it's absolute peak, lactate threshold fitness can only be sustained for a fairly limited amount of time.. about 4 weeks. It takes roughly 6-8 weeks for a well trained (ie: aerobically fit) athlete to maximize their lactate threshold. What I see happening with an athlete trying to run tempo every week is a plateau fairly short of their race.. then a slow decline in tempo speed. Your body cannot improve on 23 weeks of hard running. The time frame is far too long.
In many circles "speed work" is 100 meter-200 meter sprints.. this is something we all should be doing and will not mess with aerobic base building.