I've come with a pretty much simple idea.
Keeping track of every builder's "scores" in ALL tournaments.
It should keep track of : total number of KO's/TKO's/WBP's your robots got in tournaments, but also total number of losses, as well as total number of matches won/lost.
If we begin with RAW, for me, it would be: 4 KO's, 1 TKO's, 0 WBP's, 4 losses, 2 matches won, 1 match lost.
Comments and criticism welcome.