I've actually begun making an attempt on updating this and the rest of the Picker mods to 2.0, and so far have actually been making some good progress. I fixed the error above by simply commenting out that entire for block (it doesn't appear to be critical for mod functionality, simply used for error checking and "script protection")
All of the other changes I've made so far are simply updating prototype references during control.lua to match the new format (from game.x_prototypes[object] to simply prototypes.x[object]), removing the "hidden" flags from all of the picker added tools, updating the picker tools to the new "select" format, and one check to ensure global variable exists before attempting to write to it.
So far, I've got Picker Extended working perfectly, except for the testing map (which I don't really know how to fix, but it doesn't crash unless you try to open it, so I'll probably just ignore it for now). Not sure if I should release them via OneDrive or Google Drive, or actually upload them to the mod portal as entirely new unofficial updates though. Don't know if I want the responsibility of all the other mods that depend on this one...