No one can prove beyond a shadow of doubt that Froome is doping, granted. But what we can say with certainty is that literally overnight he experienced a dramatic, essentially unprecedented increase in weight/power. Despite Sky’s chicken-****, hypocritical refusal to publish his power values, we have enough data to make this claim. This is what has to be explained.
He didn’t just become a better climber or tactical GT rider overnight. He also became a much better TTer, consistently several % faster, which represents a huge increase in power. Even if he was able to lose several kgs without any loss in power, which is highly dubious, this would not improve his TTng that much. This improvement demands a large increase in raw power, I just don’t see any way around it. And this increase occurred at a time when by his own words he was losing weight, and at the very best, would hope to maintain power, or minimize loss of it.
So the argument that he came from a poor background in cycling, and his talent only became manifest after working in the Sky program, doesn’t work. Even if he had extensive work in a wind tunnel—and on the contrary, Froome has said he never spent any time that way—nothing Sky might have done to improve his bike handling skills would allow him to go from at best an upper middle of the pack TTer to one of the best in the world. OTOH, we have in recent years seen a number of climbing specialists suddenly make similar large jumps in TT performance—Heras, Basso, Contador, e.g.—and in every case we have good reason to attribute that to doping. We also saw LA go from a decent TTer to the very best in the same way.
The schisto argument also fails. Froome has never provided a shred of evidence that the disease impacted his performance; on the contrary, what evidence we have been able to piece together from his somewhat inconsistent stories indicates that he was basically the same rider before and immediately after the period during which he probably contracted the disease. We have also been told that the disease did not affect his blood values.
He says he was diagnosed and first treated in December of 2010, yet he still did not exhibit any major improvement in his riding in the following year, until the Vuelta. He claims that his first treatment, indeed several subsequent treatments, did not cure him of the disease, though several authorities on the disease have pointed out that this is virtually unheard of. Moreover, even if this really is the case, the timeline doesn’t back up a story of the disease inhibiting his performance. He had a second treatment shortly after the 2011 Vuelta, despite being at his maximum performance level in that race. He blamed a chest infection in early 2012 on the disease, yet he rode fine at the TDF that year. He also rode well at the Vuelta (taking into account the effect of the previous Tour), and all through the 2013 season up to and including the TDF, yet he claims he still wasn’t cured of the disease and had two more treatments during this period.
So we’re supposed to believe that Froome, virtually unique among individuals with the disease, was not cured until he had four treatments. Because of this, the symptoms were constantly returning, yet except for one period in early 2012 that was not critical to his schedule, they never came at a time when they affected any of his racing. This is in sharp contrast to pre-2011, when, the story goes, the disease was affecting his performance all the time, and without his even being aware of it.
So how could Froome achieve such a remarkable transformation through doping? If he was not blood doping at first, or only at a very low level, I think a stronger program could explain his TTng, just as it has other riders. I don't find this part of his transformation so difficult to understand.
I think his climbing is harder to explain. He's very tall for a rider, a body type not naturally suited to mountain goats. Weight loss drugs could be part of the answer. This would also explain his increasing fragility. Remember, even Walsh predicted that Froome’s days at the top were severely limited. But even so, I find his transformation as a climber remarkable, and the most difficult part of the story to explain, even assuming doping. He remains a puzzle to me.
Edit: Just had an inspiration (I think). If Froome's story is ever made into a movie, the actor I'd like to see play the Dawg is Jim Parsons, aka Sheldon on The Big Bang Theory.