In the game Star Fleet Battles, photons and disruptors have a limited range -- still tens of thousands of kilometers -- so this idea doesn't work.The fleet warps in to the edge of the system, maybe even the Oort Cloud out!
Your launch say... 1000 torpedos (big fleet) the torpedoes acclerate to near lightspeed, then coast in. Depending on the distance, take a few hours to get there. aoubt 15 seconds before they hit, they come alive, and acclerate to target, ether updated by the ship, or if jammed, there own guidance. Boom. then you warp in and clean up!
However, comma, the game also has drones (missiles), and they have a special long-range drone that do work exactly like that.