Which right seats? What equipment? What do you do when there's a furlough? What about stagnation and the impact this has on mid-level seniority F/O's who can't hold CA, but want to bid bigger equipment and can't? How about the F/O who can't hold a line because there's a new F/O senior to him? Who makes up his loss in pay? Are you going to re-write the CRM curriculum to address new CA's flying with former CA's?
Let's talk union politics. Suppose in order to placate the top tier of F/O's that may get a chance at CA by continuing the injustice known as AGE 60, you have a new demographic of F/O's: 1) Those who can't get off of reserve because of your scheme 2) Those who move up a little, but are still facing the glass ceiling of widebody equipment because of your scheme 3) F/O's who used to be CA's but are thrown a "bone" which still punished them for the crime of turning 60.
Can you imagine any of these people showing loyalty and allegiance to the CA's in the union? This civil war will result in roll call vote after roll call vote with the F/O's taking every possible opportunity they can to stick it to the greedy CA's that came up with and sold this idea to the FAA and congress.
Conversely, we can take this rare opportunity of burgeoning prosperity at the airlines and do away with Age 60 while upgrades due to expansion continue. If there ever was a time that this rule could be changed with the minimum of pain, it's now.
Flop, you need to return to Lav A and continue working this idea of yours out, bud.