Machining a hub out of aluminum would be a straight forward project. You want to use techniques that avoid stress risers in machining however. Width of the
flange would have to take into account the width of the spoke head curve on the
wide side and strength/resistance to deforming under spoke tension on the thin side.
If you use atypical spokes as more and more uber wheels hubs are doing then the
design is up to you. Hubs should not flex. Aluminum in particular does not do well
in a flexing mode. Flange height is arbitrary as well and radii from axle center to
flange OD have been upwards of 35mm. Larger would likely just add weight without
performance advantage. Smaller is limited by your bearing size. Flange distance
apart has some arbitrariness also but narrow flange spacing with long axles is likely
to result in a wheel with a bit more side to side flex than a more standard spacing.
Wider triangles add rigidity to side load on the rim.