About six months ago we repaired a Zipp rear wheel for Mitch. He was really happy with the service and the build, so he contacted us for a training wheelset for his Titanium rim braked road bike.
He was particularly interested in the Mavic Open Pro UST rims, as he wanted a light rim, and a reliable tubeless profile.
The Mavic rims are certainly very light, they do tubeless well, and their brake surface is lovely. The only downside we see is that (due to their low weight) getting the wheelbuild right requires time (and experience) . Primarily to get the right tension without going too far. We always install a tyre and do final tensioning and stress relief, and dish with a tyre inflated to riding pressure.
Mitch chose some Velocity mid level hubs for super reliability, and the robust steel freehub. In our view, the best place to put a little extra weight is at the hubs. With such a light set of rims, this cost conscious build will still feel very spritely out of the saddle, changing direction, and sprinting.