The problem being in most cases it's merely a novelty as it's hard to really find a good niche for legs. One asks "What major advantages could legs have to make them worth adding?"
But I've been thinking for quite a while, and I think I've got it.
First, the design. I've thought of the design, something that would work with Warzone's graphics and when animated would not look terrible, I would think. Most leg designs are mech-like or Star Wars walker-ish, and I think that's the wrong direction.
This, to me, is more practical, and it should be fairly easy to animate without looking too lame in Warzone. The spider/insect "splayed" posture should be excellent for what I have in mind. The drawing I made is minimalist, the legs would of course have more detail, but that would be their basic posture. Sadly I lack modeling or animation skills so this is the best I could do. I think perhaps heavy bodies should have 6 legs and/or thicker legs, and simply thicker legs for medium. Super heavy maybe eight or just 6 thick legs.
But most importantly, the attributes. Firstly, I'd say give it the lowest weight support, lower than even hover. Next, it should have the best all-terrain abilities, on par with cyborgs. It's body points should be lowest of all, lower than wheels, even. It should be more expensive than tracks, and have medium speed, perhaps in between half tracks and wheels, or maybe faster than that.
But here's the kicker...it will be able to scale cliffs.
By cliffs, I mean:
Yes, terrain unnavigable to any other units (not counting VTOLS, obviously). This will give them an extreme advantage. I do not think this is impossible to animate, because I see vehicles near cliff edges all the time at an angle, so allowing a vehicle to traverse cliffs should not be impossible (besides, we have the source code, so that should mean hard coding doesn't matter, correct?). I believe when scaling cliffs their speed should be cut in half, that should be fair, I would think.
This massive advantage would be balanced out by the aforementioned low armor, terrible weight support, and relatively high cost to manufacture. They should also have weakness to AP the same way wheeled and hover units do. Perhaps having literal weapon limits on legged units, as with VTOLs, would be a good idea, such as not allowing legged units to carry heavy artillery (like Archangels or Howitzers) or heavy cannons/gauss cannons.
I don't know if such requires creating a different set of weapons specifically for them. I know VTOLS have that, but I don't know if that's -only- so the VTOLs have their own versions of weapons with higher firepower, or if that's also required to limit. Ether way, I'll continue.
The strategic and tactical uses of legged propulsion would be quite interesting.
Light/medium bodied walker units with anti-tank rockets perched on cliff faces to take out tank formations.
Sensor walkers finding a high vantage point to get a good survey of the area, or to direct an artillery strike.
These could be a turtler's nightmare as well, as many turtlers take advantage of terrain (many maps have bases with a few or sometimes just one entry point).
I can also picture mobile AA walkers on top of cliffs...the uses are endless.
This is, I know, a very drastic proposal, but I think it's a unique idea in it's own right, and deserves some consideration.
Now we need stun lasers. 
