As I keep reading here, and as seems obvious at a glance, the Coker wheel isn’t that strong - or, more accurately, stable. Th problem is it’s a massive disc with a narrow hub, so that the spokes on opposite sides are nearer to parallel than they would be on a smaller wheel. There’s plenty to stop the wheel going egg shaped, but nothing to stop it going pretzel shaped.
Years ago, I rode a penny farthing with a wheel that was about chest/chin high to me (probably a 60 inch?) and the rim was very narrow indeed, with a solid rubber (or similar) tyre. The difference was that the hub was a fair bit wider than on a modern unicycle, giving the spoke pattern more width, and the rim more lateral stability. The disadvantage was that the pedals were further apart, encouraging a rather bow-legged pedaling style.
It strikes me that the only distinctive thing about the Coker is the tyre/rim combination. Coker make the tyres and tubes, and the rims (or equivalents) are not available from elsewhere (correct me if I’m wrong). The frame is fairly standard except for length and everything else is bog standard.
But… if there are people clever enough to make geared hubs for unis, surely it would a ‘fairly’ simple task to make a hub say 1/2 as wide again, giving the spokes a wider angle and making the wheel easier to true, and more rigid. This would in turn necessitate a new uni frame with a wider crown and the forks further apart, but as the Coker frame is nothing to write home about, and there are plenty of frame builders out there, I doubt this would be a problem.
So what I envisage is a Coker with the hub maybe half as wide again, and forks suitably spaced to accommodate it, producing a ride with all the benefits of the big wheel, but with more structural stability. What does anyone else think?