According to the specs, the 3200 is actually a better pack than the 4800. The 3200 is a real 20C pack and is capable of delivering 60A of current. I doubt that the nimh pack can do that without significantly dropping voltage. The 3200 will likely give you more punch with the nimh pack perhaps giving better runtime.

Trakpower has a balancer for their packs. Perhaps it will work with the Orion packs too. As for making an adapter, I don't see why not. I thought that I had seen someone post something about it at rcgroups.