There is a scoundrel talent from galaxy of intrigue (bomb thrower?) that is (almost) ideal (you can build grenades from some stuff in 6 seconds, and gain a bonus to handling explosives) iirc
Then there is the saboteur prestige class from force unleashed, if you want to invest further in that concept, the military engineer and the improviser might also warrant a look.
Also: depending on how mines are interperted to work in your group, you may want to take a look (they can be found in force unleashed and galaxy at war)