In doing some more research it seems that some devices will do WDS and WPA, though I wouldn't trust vendor-specific implementations of it. Both my devices probably support WDS and WPA, but interoperability between the two.. I have no idea.
I do not believe powerline networking will work for me, as my networking room is on a different 120V Leg than the room where I have my WDS node. The way I understand it (Admittedly, not very well) the signal would have to travel to the transformer on my street and back. I know they're on separate legs because I have an extensive X10 Home-Automation system setup, and I had to buy and install a specific repeater to allow devices on each leg 'talk' to each other. My X10 devices would, at best, work 25% of the time without the signal bridge.

I might try buying some plenum Cat5E and drop it down an airduct, or just concede that I wasn't meant to have wireless in my whole house