Pure Demoknight isn't OP though really. Barely anyone even uses a pure demoknight setup, it's just that the booties compared to the grenade launcher is really no choice. As for the caber though, i'm not really suggesting anything to make it useful so much as fun. A recharging caber is more fun than free cocaine. I'd actually prefer a caber that does 0 damage and recharges than one that does 2000 damage per hit.
About the Wanga Prick and YER, I don't mind using them as they are...but the disguise annoys the hell out of me. Most of the time it disguises as engie and hale thinks you're stranded and need killing. It's pretty much useless in that department but I don't think anyone really minds that to be honest.
Only of those changes I would really even want are the Caber, the Zatoichi, and the Short Circuit. Just because those all are fun weapons that barely get used.