Ehh, straight up cop might be too much. You'd get a straight up or down every night. Even assuming D1 NL, that's 1/3 of confirming an opponent for death, 2/3 to confirm that you're better off lynching that Townie. That said, as is you have de facto copping, because a failed shot means they're probably Town, a successful one gives you a flip.
Maybe if you give each team both a Watcher and a Roleblocker, and don't restrict them to using a power or making a kill. The added scum power is actually to Town's benefit, as it merely adds to the scum vs scum play. Watcher can catch the opposing team, Roleblocker adds WIFOM and doubt to negative Watcher results and failed kills. Did the shot hit BP? Was the shot blocked? Etc