I've not had a chance to go over all the combat rules in the book, so I may be missing something here with my suggestion.
First, I understand being unable to wager something you don't have. But it seems odd that someone can't take a wild swing unless they have an avoidance of 3 or charge an opponent unless they have an avoidance of 4. I'd rather all characters be capable of such things, with an appropriate consequence if one can be found. There may not be an appropriate consequence here, hence the 'cant wager what you don't have'. But I do have two suggestions if case you like either one, or parts of either one.
1) Have the rule preventing people from making wagers or taking actions that would reduce their avoidance to 0 or lower. Add an option for a Hero Point to be spent to let a character take an action that would reduce their avoidance below 1, and along with the action, their avoidance is reduced to 1 instead.
2) Allow avoidance to become 0 or even a negative number. Attack rolls still require at least 1 success for a hit. Like normal, excess successes on a hit add to the attackers damage roll. So an attack roll with 1 success on a target with a -2 avoidance would have a hit with 3 excess successes. Characters with an avoidance below 1 cannot take actions that would further lower their avoidance. Yes, this would devalue armor somewhat, but so what?
Obuasi Okoru - Altherian Priest of Althares and Career Academic Student
Jacob Bartlett - Gruff Woodsman, Stalkers of the Unseen Hunt