Squad movement is looking ok now.
Given solid pathfinding code and physics, it was already working reasonably well in that units could simply push other units out of the way to get where they wanted to go. It just didn't look that good. I chose a simple solution; as my squads are quite small I don't need anything too sophisticated.
First I predict collisions using a circle intersection test. I only care about the next predicted collision. The unit's path is deflected either left or right depending on which requires the least deflection while still leaving room to pass. Once the collision is no longer predicted, the unit returns to the original path. It's nice because it's sort of self-correcting, and doesn't involve modifying the path or the path-following code.
With that working I could move on to commands. I currently have three: move, follow and attack. Because I'm using a component system, each command is a component. Follow and attack both make use of move. It's possible to use these components directly, but I wanted to have a queuing system for setting up waypoints and general automation. How to handle that? Another component of course! The command queue sends messages to the other components to begin and end actions, they carry out the action and respond with success or failure messages.
For the commands in the queue I use a Command base class with virtual functions. This makes it easy to plug in new commands. But most of the work is done in the components.
This could get interesting if I start mixing it with AI. How much intelligence should an individual unit have? I want some of them to not even have the pathfinding component, so they could only follow or attack within line of sight. My attack command is very basic at the moment. It could take into account cover, different weapon types and the current health of the unit.
Next, though, I think I really need to make a proper level. It's just been small test areas so far and they don't have enough scope to try out these ideas properly. So I shall put on another hat and become a level designer for a bit.