Although this would be convenient, I think the compromise of one filler has been well thought out.

The second filler would easily add $200 just in parts. Probably twice that.

I believe it's hard enough for designers to squeeze a gas tube into most cars anyway. Quite a few cars have the tank under the back-seat. In many of these the filler tube occupies one-side while the exhaust system is on the other. You really can't have the exhaust pipe near the fuel filler--you don't want to impart heat to the gas first because it's more dangerous, but second, because it can vapor-lock and cause the engine to die.

I know that the older cars with the filler straight in the back were easy to fill, but since gas tanks aren't in the back anymore and I believe there are safety issues with the filler, this has gone-away.

Maybe the compromise could be putting the single filler-neck in the center of the trunk-cowling, right at the base of the back-window? At least in smaller cars this would be easily reachable.

Also, I really like cars that indicate which side the filler is on right on the gas-guage.

1.) purchase permanent black marker.

2.) mark fuel guage with arrow indicating which side the filler is on.

Personally, I use Post-Its to remind me where the filler is (I own and drive several vehicles). This has the added benefit of really annoying the heck out of my 34-yo daughter...

This is a good idea but what i would do is work on the gas pump side and make sure they are compatible to the gas side of the car. what i mean is the gas line or the pipe shud be extendable to the other side in that way we work only on the pump stations and all the millions of automobile wud be integrated

This used to be a common feature on Jaguar sedans. Seems simple enough.