Salvage and Reprisal are exactly the same thing. You could call it Player Salvage and AI Salvage really. The player and the AI just buy ships differently, but the way they salvage is the same (isn't it? Perhaps I'm mistaken here but that's how it feels like to me).
I think you should keep it. If there's no salvage/reprisal, why wouldn't I just dump Neinzul through a warpgate all day? It gives an incentive to retreat and improves tactical richness. Black Hole Machines are useful. There's incentive to barricade warp gates to force enemies to perish in your territory. There's incentive to upgrade your command stations.
Here's a related idea I had: Mining Outposts
How about giving us a building that is immobile, somewhat like a Neinzul Regen Chamber, but it spawns mining drones which are very slow and defenseless. When ships are destroyed, have them leave actual visible debris, which those mining drones will go mine (cut useful bits off of) and take back to the Command Station. This is your salvage. The AI can also build this structure, and those drones give it their reprisal bits. I could use science to upgrade this building to improve my salvage percentage, or their speed, or their numbers, or whatever. I think this would give planets a more "alive" feeling, having these little automated drones flying about doing useful things.
Players could wait for a battle to end, then build the Mining Outpost to get the salvage.
Bonus idea: The mining drones would also be the units that mine resources from the planet (see some other thread about planets) for the player and AI. Maybe they could also be the units that load the trains (see some other thread about trains).