So any thoughts on how could I make this idea cooler?
My thought was that maybe the trolls make off with a few really power/nasty/evil/bad artifacts that the happened to be in the shop. Sure, the PCs save the shop, but the last few trolls see that they are beaten and just grab a few things and make a run for it. Then you can run a follow-up adventure where the party has to track down the trolls and/or the missing items.
I can see it now: "By the Gods! Those trolls made off with the Pitchfork of Asmodeus! Of all the dumb luck, why did they have to take that! We have to get it back... no telling what might happen if THAT falls into the wrong hands...."
I know it doesn't seem like where the discussion is going, but you might be able to use this idea in addition to everything else that's going on...