as said in the title, have multiple lair pathways overlap with one another at points. so two teams of 5 start at two different starting area's and as they go along the lair paths they intersect at points, such as having marines fighting on a bridge, while being able too see a bridge below them where an ork team is fighting in a different direction. or have eldar going through the sewer sections, to see a squad of chaos marines going the opposite way through the grates. they wont really be able to interact (though in the future that could be changed) but they could easilly trade pot-shots at each other at certain points. mabe even have they're lair paths converge into a boss battle arena to take down some big nidzilla at the end.