Electric Bikes - Derailleur, chain, and shifter parts for rear-hub conversion

Okay, guys, this has been playing out in my mind the last couple of days. I'm set on doing a rear-hub conversion even though I know a front one is much easier and cheaper to do. Plus, there is that weight balance if you do the front hub. It looks like most electric rear hubs either come with a 7 or 5 speed. I plan to get the Ampedbike kit, which comes with a 5-speed cassette. I will need to get a shifter, chain, and derailleur that are compatible with it. The problem is that finding these parts in 5 speed is sorta hard. I found some shifters on ebay (Shimano thumb shifters and Nashbar has acheap one) but they look dated and cheap. I'm still looking for a rear derailleur that is for a 5 speed. There appears to be some Shimano ones but again they look dated. I'm thinking of building the e-bike from the ground up, starting with an aluminum mountain bike frame (no rear suspension). I want to have good parts but not too expensive as it will be a commuter and runabout. For those who have an electric rear hub, what is your gearing and shifter set-up?

I was under the impression that the spacing on a 5 ring cassette is probably the same as your regular one. In that case, all you need to do is to adjust the limit screws such that your bike only uses the 5 rings. If the spacing is different then you need to replace the index shifter.