Originally Posted by IPassGas

You want a disc brake. I presume you mean a ventilated hydraulic brake ($$), because a standard disc would fry under your conditions. You ok with bleeding the brake, carrying fluid and topping off on a long tour if needed? You will need to change your shifter to be compatible ($$). You have a derailleur from the pictures, consider instead changing the rear hub to something that can accept a drag brake. May still be possible with phil wood, don't know. Our older santana toured through many mountain passes loaded with camping gear and food on dyads with a drag brake... never a problem, a drag brake last for a very long time with little maintenance. But, it is not disc brake sexy and bike companies like to sell stuff.

Tubeless...you tour off road in goathead country or on interstate shoulders often? Otherwise why bother. And even then, higher pressure tires and tubeless do not go well together.

Our newer tandem has a son28 and rohloff. I agree with rick, andra rims are the best. However, you are focused on the front wheel, 36 spokes are ok in front since it is not a dished wheel. Velocity rims are good.