I just had the same need, for my Saga Disc. I choose tubeless ready mountain bike rims, SunRingle Helix TR27. Only 520gms, stronger than my 599gm Mavic a319 rims and 80gms lighter. If you are using rim brakes I'd still use Mavic a319. I used straight gauge 2.0mm DT spokes, Shimano XT756 rear hub and Shimano 3D71 dynamo front hub. I didn't bother to try to find 36 or 40 hole rims and hubs, these wheels are as strong as my 29er MTB wheels.
The new tubeless ready disc rims have a much better design compared to older hookbead clincher rims. There's less material in the beads and more material in the spoke track, the section is deeper. Stronger and lighter through proper, modern design.