He probably does, but I know that the forum meant a lot to him and I think he's probably devastated about this--and personally I feel bad that he got banned now that I know what the situation is.  I was helping him rank up by doing monthly post history reviews for him (he was one of the few who took me up on my offer), so I know he was trying his best to be productive, and I still have a very hard time believing he committed plagiarism on purpose, hoping he'd get away with it.

That's a bad idea, IMO.  If the first consequence you got for plagiarizing something was a warning, there would be members trying their luck at getting away with it left and right.  Plus the moderators don't have the time, patience, and probably even the resources to track every member through each stage of that proposed system.  They already spend enough time just checking reports and making judgements as to whether to delete posts that to add something like that on top of their workload would make it untenable.

Plus, I think that's been proposed and rejected at least once before.  I'm pretty sure Theymos wouldn't go for it.