Well, I enjoyed your post and commend you on doing your homework and providing a diagram in asking your question. Nonetheless, I take issue with that statement. For modern hubs, even if the hubs were "special" in some way, you should be able to find their nearly exact counterpart in 24h on the interweb. If they are vintage, 24 spoke setups are not gonna be period-correct. And vintage hubs were more likely to be designed for a 3 cross setup, with the 2 cross setup being more susceptible to pull-out (that is, having the spokes break the hole and pull part of the edge of the hub off). This is exacerbated by having more stress on fewer spokes. Last, keeping track of the differnt sized spokes during lacing would drive me crazy.

But you're obviously committed to this, so perhaps my objections are immaterial. Let me think it through by writing. The reasoning seems sound: the 18 holes on each side of the hub, separated by 20°. The set of holes on one side are offset 10° from each other. If you use only 24 spokes, 12 per side, then you'll have to have 6 pairs of spokes pulling in opposite directions, which means each pair of pulling spokes is separated by an unused spoke hole. Thought experiment: imagine one side of the hub setup with equal-sized spokes and symmetrical relationship with the rim. The holes in the other side the hub are offset by 10°, but the rim holes for the other side of the wheel are offset by 15. This would require two different size spokes to allow for the 5° difference in spoke angles on that opposing side. To make the wheel a little more symmetrical and to minimize spoke size difference, you propose to use different sized spokes on both sides of the wheel to "move" the rim so that instead of 0 offset on one side, and 5° offset on the other, you have 2.5° offset on both sides. Am I properly catching up to your thinking?

The question is: can different sized spokes and different spoke angles be used successfully. My first thought is that all the forces have to balance out a) tangentially, b) radially, and c) laterally. I suppose you could figure out some wildly complex way to true a wheel in unbalanced fashion so that the spokes on one side had net tangential force and twisted the rim one way (e.g. forward) while the other side twisted it backward, with torque balanced out by torsion through the hub. This seems a bad idea. Too complex, and most hubs aren't designed for that kind of torque. The hub would deflect and all your spoke sizing and such would go South. So you'd want a tangentially balanced design. In a tangentially balanced design, the spokes at different angles must have different tensions. To keep this simple, each pair of adjacent spokes would have a different tension, and all "innie" (inward pointing spokes, where the spoke head is on the outside of the hub) spokes would have one tension and one angle, and the outies have a different angle and tension. From a big-picture standpoint that would give you tangential and lateral symmetry (that is, the total forces acting on the rim aren't trying to push the rim "forward" or "backward" relative to the hub, nor to the left or right of the hub center). From the local (spoke to spoke) point of view, you'll of necessity have spoke tensions with a Low Low High High pattern. Tangentially and even laterally, these can balance out. Radially this could give you a periodic variation in rim diameter.

With modern, stiff rims this might not be an issue. They seem to be strong enough to maintain their rim shape. After all, look at the wheel offerings from many makers that use "triplet" patterns. But if you are using a more flexible lightweight rim it might give you a little periodic variation in rim diameter. This is the point of my reply - I tried to separate out the different directions of force differences. Would period variation in spoke tension matter? Don't know. I suspect it could work depending upon your rim and hub. Certainly, in the other thread cited above, you see that others have actually done this successfully.

This is an interesting engineering problem. If you try it, please let us know how you made out.