looking at the active East list I count about 310 F/O's who are at or below seniority number 1800 give or take a few. Excluding the E190 we have Captains up to roughly 2100. It's rather surprising, some F/O's on the A330 could hold Captain on the B767. The number one A330 F/O is around 200 or so. So I suppose depending on where you are specifically on theoretical lists you could say that an F/O leaving is of no value to you but not to all. You must be rather senior. This airline is not growing it's shrinking. There was an Excel seniority prediction tool that provided accurate career projections to retirement after the Nic came out but it was only good till age 60. Many pilots have left since then so it would have to be revised to verify the individual impact when pilots leave. It should be clear to anyone however that the Nic award insures a significant exponential effect on the West when the East pilots leave.Of which more than a third of East attrition is out of the right seat, thereby valueless.
So out of a hundred pilots, 20 West - all capt. 80 East, 55 of whom are capts and 25 are F/Os. The ratio is 20/55 = 36%. Look at the Nicolau. Miraculously that's what the Nicolau seniority list looks like.