I got this idea from some Derro miniatures produced by Reaper. There's 3 in the pack. One has a spear, one has a club with a rope on it for entangling, and one has a crossbow. So I got the idea for a unit comprised of 2 or 3 models, working in concert. They would have what's call Staggered Activation, where you get to use the first action of one model, then the first action of the next model, until you get to the end. Then repeat the process for the second action.
Let's look at a 2 man unit doing this. The first model is armed with something to make a trip attack, and the second uses a nasty weapon to hit the opponent who's pulled prone. Model one makes the trip attack and succeeds. Model two makes a hit roll and misses (blimey!). Model one makes an opposed strength check to maintain grip, and model two finally hits. This would make for an interesting unit, but would be treated like an individual perhaps. Ideas?