Seems like something great for an NPC a party could hire to help blow something up. For PC use though, since it is rather reliant on the explosives, it might be an idea to give it a "fast craft" ability that allows members of this PrC to craft explosives and alchemic substances 10 times faster than normal. And maybe make it so for every 5 points they increase the Craft check, they can add 1d6 to the damage the explosive deals.
Myself, I love seeing PrCs that don't necessarily deal with combat. You take PrCs to get something special, and that's it. I once made a detective PrC and it had very little in the way of combat at all, besides nullifying the penalties on improvised weapons.