I've been in LE for over 15 years and have been teaching weaponless defense for the last 6 and I have to agree that there isn't one MA that is "perfect" for law enforcement officers. I like to think that we (meaning my department) have one of the more comprehensive weaponless defense training systems available. We teach arrest control and compliance, Krav Maga for self-defense and ground fighting and the training is on-going versus the once every two years that seems to be standard in our industry (I hold class about every 5 days). I like KM for the self-defense and given the situations that it's used in, it doesn't require modification in order to be effective and the National Training Center has worked on tailoring their techniques to a LE application. But, it doesn't have a lot in the way of arrest control but then again neither does any other MA. BJJ or Judo is great for ground fighting but you have to be able to transition some of the techniques into LE applications. Same with Hapkido and Aikido and I'm sure that it would apply to any MA. There are always useful techniques you just have to figure out how to transition them into something you can use on the job which brings me to my little piece of advise....
Once you've decided on what MA you want to pursue, work with a partner or your departmental instructor and see how you can transition some of those techniques into ones you can use on the streets. As an example, we never learned a lot of take-downs with entries from the front. My partner and I worked on taking a leg sweep and a hip toss to a prone control so that we could offer our officers some additional options in the event that they didn't convienently find themselves entering from a position of advantage (behind and slightly off-set).
Hope I didn't lose anyone with my rambling. I'm at my in-laws and keep getting side tracked by other conversations.