Newbie needs advise

Hey everybody, I'm getting into serious research mode for a new pup. I would greatly appreciate advise on which breed to go with...here's my scenario.

I am with a military man, and move around rather frequently. My primary purpose for getting a dog is for personal protection (and of course, companionship when my man is away ). I am willing to put forth a lot of time and $ for training, and am considering making my dog a service dog (opinions??). I have experience training, but would not call myself an expert. I've grown up with everything from labs, mastiffs, dobies and pits, even a wolf hybrid. I have been looking at Belgian Malinois, but am afraid that they require such a high level of physical exercise that if I am at work 8 hours a day, he would suffer from boredom. Mostly, I am looking for a dog that is trainable, intelligent, and has high energy levels without risking depression if they don't get enough.

Thanks, guys!