Which MOS within the intelligence community would set me up with the best options post-military?

It would be better if you focused on the career field and your duty for the country.

That depends on what you want to do post-military in those organizations, because they are different. And, even within those agencies, there are also different jobs. Do you want to be an investigator? An analyst? An intelligence collector? An intepreter? Your question can be answered more easily if you let us know what exactly it is you want to do.

1) Instead of focusing on how a MOS will benefit you, you should focus on how you are going to benefit that MOS and the peers you’ll have to your left and right and the personnel on the ground you’ll be supporting...
2) Having the job doesn’t help get you into a career outside the military. It’s the education that you obtain and the experience and time in the job that gets you looked at for the civilian job. No matter what the job is (Especially in the Intel World)
3) As a possible recruit, I wouldn’t be worried at all about what is going to get you the good job outside the military, I’d worry about researching what is entailed of you to even graduate the AIT to be MOS Qualified. (People join the Army and look at the name of the job and don’t research the job and either wash out in AIT or get “pushed” through AIT and then go to a unit that supports real life missions and don’t know how to do their job, because they picked a job that sounds cool and end up in over their head.)

Do your research. But to answer your question: As a person that has any Intelligence Background (No matter the specific subject) with experience usually 3+ years some more you are opened up to many jobs in the Alphabet Soup career field.