Currently there are two settings for military squads; stay close to station and chase enemies.
What if there were a third option? Something that would turn a soldier basically into a hunter, or at least the same kind of behavior, chasing enemies all over the map, and getting aggro on the enemy the instant it steps on to the map?
This offers intriguing possibilities for soldier-based defense on open maps, where you cannot rely on choke points to defend, or if there is very hostile and dangerous wildlife that frequently visits the map, and hunters just aren't up to the task. Continually invaded by hordes of zombie elephants? Set all of your soldiers on search and destroy, and they'll seek out these extra-evil elephants and deal with the matter. Hopefully. Or there could be horrific carnage over bloody socks.
And by adjusting hostile or neutral to wildlife, dwarves could function very similarly to hunters, or they could ignore the wildlife and only chase down things such as goblins or dragons.
The upside to this is that it would allow a more hands-off approach to fortress defense, particularly for open fortresses that don't rely on Choke Points of Doom(tm) as the entrance, and the soldiers will more aggressive take to the field to do their thing.
The downside is that soldiers would scatter in all directions to hunt down goblins, as goblins appear all over the map. However, this could also be an upside, as right now multi-legendary dwarves are nigh-unstoppable killing machines. Sending them out, possibly alone against an entire squad, would mean you're at risk of casualties. However, that just makes combat more interesting!
Another upside would potentially be the ease of adding this feature in. The code for hunter behavior is already in the game, so extending the hunting behavior and making it work for invaders and/or wildlife seems like it would be a simply enough task. Or at least, simpler than having to write an entirely new thing.