So, going back to the original intent aspect...
Jervis' original Black Legion idea was for them to have new and unique daemon engines. IIRC, this was based largely on the 40K background which said the 13th Crusade forces had lots of daemon engines, even though in 40K, the only readily available engine was the Defiler.
JJ's design concepts for the daemon engines were, imho, influenced substantially by the growing VSF and steampunk scene, which was just starting to take off back then. The Decimator and the Deathwheel were both intended to fit that aesthetic and avoid "imperial with skulls." In other words, the daemon engines are not supposed to be realistic or practical. They're supposed to be something VSF/Steampunk that fits in with the more outlandish, chaos end of the sci-fantasy 40K universe.
The Decimator was originally envisioned as a giant version of the early, WWI-era tanks with lots of rivets and an overall steam tank look to it.
The Deathwheel was an extension of a number of Victorian monowheel "bicycle" (yes, I'm aware that's self-contradictory, but I don't have a better way to describe them) designs that were later expanded into motorcycles and then theoretical military vehicles. Many of the later adaptations have a classic pulp sci-fi look about them.
MonowheelsMore monowheels Lots of the same pics, but there's a video of one of the Dynasphere.
I think the Dynasphere/Dynosphere is probably the most Deathwheel-like of them. There's even a version with a (supposedly) 5-person cabin that extends off each of the hubs.
The "gearbox" style that Mango brought up would fit very will with that steampunk/VSF aesthetic, imho. I could see a baroque mesh of gears filling the center of the Deathwheel like classic clockwork tech. I could even envision a model that meshes that clockwork concept with the aesthetic of the more recent 40K daemon engines - something like the organic curves of the dynasphere cowling turned into semi-insectoid armor, with glimpses of the interior clockwork visible in places, like the exposed workings of the Defiler or Brass Scorpion.
Another option would be a di-wheel, with 2 parallel monowheels linked.
DiwheelsThe Vereycken diwheel or the Swedish diwheel look to me like they could have the most "practical" military adaptation. With the 2 wheels butted up against each other, it would look like a single wheel, in keeping with the Deathwheel concept. It would be able to maneuver by spinning the wheels at different speeds, just like any tracked vehicle.
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On a sidenote, Jervis also made the point that he didn't want chaos titans in the list. His story was that the Heresy background was largely written as a civil war primarily because at the time, two identical forces against each other was all GW's production capability could support. He wanted to move away from that and distinguish the lists more clearly from Imperials. He only relented and allowed the chaos titans when it became apparent that there would be no chaos models, and thus none of the new daemon engines.
