I sometimes speculate on what some weapon designer has up on their whiteboard using an F9 booster as a weapons platform. What is the range of a Tomahawk launched at 80,000' and Mach 3? Or a cluster of 9? Kind of scary when you think about it.
Tomahawks have air breathing turbojets that wouldn't function at 80k feet nor at speeds much above 5-600 mph. They're also not stealthy - they're designed to fly low to evade detection, and have conventional warheads. IMO, SpaceX rockets don't really have,any advantage for delivery of ordinance vs existing systems, and using them for attacks in anything less than a full on world war just makes every civilian launch into a potential flashpoint for war.