I ran the poploc on a Reba Race for a few months. While it is true that the lever is plastic, I never experienced any problems either with the structure of the lever or with the location. If you look how the lever is mounted, you see that you can place it mostly out of harms way.
My brake levers are struck often with branches and on unexpected dismounts, but not once did the poploc strike anything. That being said, I abandoned the Reba for the WB Magic IMV and find with the stable platform that I rarely miss the remote lockout feature.
As for other remote systems, I know that Cannondale once made an ELO (electronic remote lockout) for certain Lefty forks. They appear every so often on ebay.