Big Biff
Got Em
http://www.marines.mil/news/messages/Pages/2007/Messagesa64.aspx
Correct me if I am wrong, but I am pretty sure to try out for recon you must go through SOI, no matter what your MOS is, and if you fail the indoc or training then you are put back to 0311. So why enlist in another MOS in the first place if your intentions are to be a 0321?
Going through the 0321 pipeline would definitely give you a leg up to getting into MARSOC in terms of experience, but understand that you are not going to earn a slot in MARSOC by just getting the 0321 MOS. You still have to do a few deployments and then tryout. Then you have to pass the three week tryouts against the hundreds of other applicants from all crawls of the Corps ranging from guy admin pog's to female helo mechanics.
By the time you were elevated to Operator status you would be a 23-25 year old Sgt and be expected to again complete a few deployments. After this you would be around 25-27, then IF selected for MECEP on your first try, you would do another 6 months in the prep course, then (assuming you have no college) another 4-4 1/2 years in college putting you between 28-30. Now you are pushing the limits with waivers as to whether the Corps will let you fly.
It's like everyone else says, if you want to go flight, that is good to go... If you want to be Ricky Recon/Super Secret Squirrel that is equally as good. Who knows, whats to say you got selected for MECEP after being an operator that you choose to be a team leader in 03 or MARSOC. I would think this would be more realistic than hoping the stars do align for that brief moment in history and you become the exception to the standard.