To make scrapyards even more awesome, since they don't seem to replenish resources, is to make a sector rule that if a scrapyard is present, all large wrecks (15 blocks or larger in 1.3.8) don't have a de-spawn timer, but all wrecks de-spawn normally. This could allow players (or an NPC tow service) a place to dump wrecks of ships that are not being rebuilt. Otherwise, on multiplayer servers, once a scrapyard is depleted, it's depleted and the primary function of the station becomes moot.