RM,
Given your stated priorities and the fact that you wanted a carbine to shoot for so long, I would also consider a few other things.
One is how good does your carbine shoot in the RMC stock? Collector value aside, the fit of the stock (recoil plate and barrel band) are the key to accuracy and shooting. And like a pair of shoes, they all fit just a little bit different in those key areas. You do not know how good a different stock is going to fit and shoot with your receiver/barrel. Selling a stock that fits for a hand full of cash will not guarantee that you will find another stock (regardless of the manufactur and markings) in the future.
A second point is to consider what value YOU put on the current stock. We all have read your posts as you have receive this current carbine, had trouble with the cracked stock, and then got excited at the replacement CMPsent you. There is some intrinsic value in that experience.
I also agree with Charlie that you should save the RMC and use the M2 for shooting. Remember, when it comes to carbines, they don't make the real stuff anymore. If it ain't old, then its a repro...
Just my two cents worth....