1) The fact they are lining guests in backstage areas is completely and utterly against company policy and I have no idea who is directing it be used in that way or why.
2) In DLR (not WDW), that area is not where the restaurant would go. The restaurant would go in the SW section of the Resistance area (unless they have changed it since my last time seeing plans). That area you're referring to is one of the last remaining attraction expansion pads accessible for future DLR additions, so it's unlikely they would have moved the restaurant plans there again. It is possible, but I would say unlikely.
The TSR in SWL is going in the same exact place (if they ever build it) in both lands, namely, the uncovered box behind Oga's. That is where the cargo crates are that is creating the overflow queue. Whether that is "backstage" is a matter of semantics since it was supposed to be "on stage" for the TSR. As far as letting guests backstage, there's a lot of precedent for that: tours, the short-lived hopper buses, letting guests out through overflow routes (such as behind both sides of Main Street), etc...