Caravan/ambassador:
Caravan is a strong card. It is pretty much a lab when you cannot draw your entire deck. I am only appreciating how strong it is not until rather recently. It works well with ambassador too.
Monument/Chapel:
I actually have thought of this one. It is actually not that hard: in the first few times when you draw chapel with silver, the correct thing to do is to trash everything else. It therefore does not make any difference (unless there is some savvy $2 cards to buy) if you replace the silver by the monument. On the other hand, in a chapel-province game, the few extra VP tokens can make a huge difference.
On the technical side, I have some trouble understanding what the ratings mean and how they are calculated. For one thing, if I open the same thing with say, LV 5 with my opponent, but I am at LV 40 and he is LV 0, now we become LV 45 and LV 5, which persumably would have a different win rate I think. (Or does the win rate depend only on the difference of the level of the players? If so it seems a rather strong assumption for the levels to follow a normal distribution.) Even for asymmetric openings, it seems very impossible for every kind of player match up to shift for the same amount for the different openings. It would be easier for me to understand if there is just an explanation of how it is calculated.