I don't know why would you need isometric/3D for that... the tactical system used in most roguelikes works very well in ASCII. That's a single character, not a squad (although against a squad), but that's not a problem.
Rebel Star/Laser Squad had a 2D system which I liked very much: when you switched to the "shoot mode", some objects changed shape: all creatures turned into circles, objects which did not obstruct the line of fire (like moon craters) disappeared. And when you shot, a straight line was drawn from your circle in some direction, and it either hit the enemy circle, or something else. (So if a small robot was on the line to a larger one, you could either shoot the small one, or miss the small one and hit the big one. You could also precisely aim the larger one off center, if you wanted to miss the small one.) That seems impossible in ASCII, of course. (A roguelike with circle graphics and straight line aiming instead of ASCII? That could be original...)