Well maybe give them a buffer period from first log on to when cheat detetion and penalties begin, like 2 days and then use the information collected to deturmin the level of the user. They could even check against online solution sites like GitHub and Yahoo. Would take some work but it would work.
Sidenote: a Ban seems like overkill

Lots of people cheat for points just to get the abilities that come with rank and honor.(Funnily, cheating gets you honor, but cheating is not honorable.)

What if it just didn't give them honor for any cheated Katas.
One way to detect cheating would be to check if some one finishes a high level Kata in a language they dont use.