Joining the Air Force specifically for an MP type career sounds strange to me, like saying I want to join the Navy but I don't want to go to sea. Serving in any branch is an honorable thing, some are just better fits for what you want out of it.
Before you worry about Special Forces and such, just concentrate on being the best at what you do and developing skills and maturity. Seems like I always here people saying they want to go in the military as Special Forces and I think someone else already mentioned the professional sports analogy. Its like saying I want to go to med/grad school to become a doctor but don't want to spend time getting an undergraduate degree where you prove you are smart enough and you will learn the skills and habits that will carry you through such a rigorous graduate school. That is why most Special Forces across the branches require a minimum rank to try out, you need a few years of service to develop that core skill set and some maturity before you can be expected to master more complicated topics. I would assume the same applies to a SWAT job, you need to be a cop for a while before you can try out.
If all you want is some a resume builder there are other things to consider, do you have a bachelors degree? They tend to help a lot with federal law enforcement. A friend of mine just became an Air Marshal, he had a degree and 3 combat tours in the Marines. Another one of my friends that only had a degree has been on the Diplomatic Security Service wait list for their academy (I think the same academy FLETC) for 6 months and is danger of having to reinterview since they keep bumping him lower for more qualified candidates.
There is nothing wrong with knowing what you want and working towards that end. You can just come off childish if your not in the military and say something like I want to join to be a Air Force Special Forces Countersniper and then get out and be on a SWAT team. Maybe you can do those things. Just have a realistic view of how few people can actually handle that, the years of dedication and service, and some tact. If you are a civilian, maybe address a combat veteran more respectfully before you start labeling "those" people. End rant.