Probably won't get much response here, but this is my dilemma. I have a tandem cruiser bike with a Nexus 3 speed hub. It has the usual 26" wheels. Anyway...I got the entire bike (Fuji) for $500 a couple years ago on closeout. The components are super low end as you could expect from that price point. The rear wheel is now breaking spokes. I had the LBS repair 6 broken spokes about 2 weeks ago and now after trying to get up a particularly steep hill I popped 3 more. My wife and I ride this bike around town quite a lot and I want a wheel that will last. Here are my options as I see it.

1) Rebuild a new wheel with a better rim using the same hub.
2) Buy a new wheel with a 3 speed hub and use the old wheel as a spare
3) Buy a wheel with a 7 speed hub and use the old wheel as a spare.

Anyway...if anyone know about Nexus hubs...are the 3 and 7 interchangeable? The bike has V brakes, but the hub also has a coaster brake. I believe the spacing should be the usual 130mm. As far as the cable...I need a long one to reach from the rear of the tandem to the front of the bike...how hard is it to retrofit a new cable if I went with a new 7 speed hub? Any other options I'm not thinking of here? I don't think I need anything greater than 36 hole since I won't be using this for long road rides, but I don't want the wheel falling apart every week either.