Lance Armstrong... greatest doper there was or ever will be

By not formally disputing the charges Armstrong is losing his ability to prevent the sanction that USADA imposes, namely the stripping of his titles and a lifetime ban.

It is an imperfect analogy, but LA is trying to make out that he has a right to opt out making himself not guilty, which he doesn't.

The reality is that he has not and cannot opt out of the sanction (lifetime ban, titles stripped)

As I said above, look at nolo contendere. The point of offering no contest is not to get out of the punishment, but to accept the punishment without admitting the facts of the case, which would then be used to support any number of potential civil actions against Armstrong. I expect there are already lawyers all across the USA lining up civil suits for all manner of losses which Armstrong's doping caused their clients, so he definitely doesn't want to make their lives easy by either admitting anything or having an independent arbitration panel come to the right conclusion after examining the evidence. For this reason, this:

If the UCI throw Lance under the bus, he will have nothing to lose and will hopefully start singing like a canary.

is never going to happen, because he still has an awful lot to lose by confirming the truth.