To get your creativity started: What's the point of lockpicking if you can simply burn down the door?
True.
Karlach + greatsowrd/great maul = open doors and chests ...
Respeccing can be fun too - Shadowheart as the sapper looks good. FOr me t was a let dwn that she no longer had the Urchin Background. But multiclassing her into Rogue - even for a single lvl for the Sleigh of Hand Expertiese - could bring that back.
For that 4th slot - Hireling?