I recently ditched the lower roller from my 2×8 HT, kept the chain sensibly short and retained the bash ring, thus far no real changes the chain stays on just fine, the next step however is probably to remove the bash as well I think, this will introduce a greater the risk of the chain heading off the top of the ring more than the bottom but the weight saving is not insignificant so it’s probably worth trying it….
I think if I was going to a 1xN setup I’d probably want the security of a both a top and bottom retainer of some sort, but for a 2xN setup I don’t think it’s actually as critical, a suitably sized bash ring seems to help stop the chain riding off the top (But obviously adds some mass) and having the chain bounce on to the granny isn’t as much of a problem as having it bounce off all together…
As for simply Not Back-pedaling, in my view you should be able to do it, it’s not “incorrect technique” its setting your pedals for whatever corner/obstical you are approaching, can’t see why anyone would accept not being able to back pedal other than if they were on a fixie…