From my point of view, the main problem resides in the fact that challenger TT threads are buried deep within the games section of the forum.
The other TT threads are much more easily reachable. There must be a way to do this with challengers.
That's a very valid point, and one which I have raised myself (and I am sure others have as well before me)
Apparently it is an MTF problem rather than a TT problem. As I understand it, they are not willing to have a sub-forum for each challenger, and therefore if TT threads were put into the challengers section they would be mixed in with all the other threads relating to challengers, and it would probably be even more difficult to find the right place than it is already.
My point would be that if a player is able to find the right thread to commit in, he should remember that he has done so, and send his picks.