The rim doesn't care what kind of hub you have (except for disc brake specific rims), so all that matters is the hole count.

I'd build this bike with something like a DT Alpine single 2.3/2.0 spoke on the right rear, and Alpine-3 2.3/1.8/2.0 for the left rear. This will maximize elbow strength, while having the left flexible enough not to require very high tension to stay tight. If replacing both hub and rims, I'd look for 36 or more holes, but IME- that tends to reduce selection too much so sticking with 32h on a stiff rim may be the best option.

For rims, look for something with good rigidity, that will work with a wider tire (probably the best improvement). You also want a rim rated for fairly high spoke tension because heavier loads increase rim deflection at the bottom. If possible, build to the higher end of the working tension range, something like 120-140kg or more on the right.

As i said a wider tire will definitely make a big difference.

The other thing you can do if he has a steel frame, is to increase rear triangle width to 135mm, and add a 5mm spacer on the left to reduce the amount of asymmetry (dish).

That's all that you can do, but the rider is part of the equation. IME rider habits have as much to do with wheel issues as rider weight or build quality. BITD I rode with a ballerina who would destroy wheels routinely, and a 240# or so who rode like a ballerina and could make lightly built wheels last forever. Learning to stand and use legs as suspension to help the bike over bumps, not overly rocking the bike side to side while climbing and/or pushing overly high gears will help this rider get more life out of any pair of wheels.