I love dynamo hubs, and I strongly dislike batteries. So while @
clasher may be right, I vote dynamo hub. The SP hubs are quite nice.
As for rims, I have no experience with the Soma Weymouth rims, nor the Velo Orange ones. I recently got a pair of the Pacenti ones, and they are
really nice. I am a cheapskate by nature, and have no regrets about those rims. Unbuilding my old wheels and rebuilding them with the new rims only took a couple hours. My Pari-Moto tires seat much better on the new rims than they did on the old ones (which were Velocity Synergy or some such name).
The thing about rear wheels, and the heavier rider, is that the wheel has to be severely dished to make room for a cassette with 8 or more cogs. This means a lot of tension on the right side spokes, and a lot less on the left side spokes. On a wheel that isn't dished (such as with a Rohloff hub) 32 spokes is plenty, even on a tandem. Some rear rims are offset, so the spokes are left of center, which evens out the tension a bit. There are also wheels that use more spokes on the right side than on the left. Such tricks make for a stronger wheel. But as for 32 or 36 spokes, I think it's ridiculous to worry about the weight of four spokes. Go with 36, or 40 if you can find a 40h hub and rims. Why not?