What do you mean by buff or make viable? It's easy to say "this needs a buff," but if you don't say how, it's hard to judge your idea. The thing about sidearms though is that you only use your sidearm when you lose access to your main weapon (ex: your katana is knocked out of your hands, you draw your wakizashi or you are an archer, so you draw your sidearm in melee). Sidearm weapons are not supposed to be as good as main weapons or they wouldn't be sidearms. I don't think buffing them would add anything to the game. The only result I can see is that they are buffed enough that people would use them as a main weapon, which defeats the purpose.