You nailed it!
From the System32 folder, I had to add:
msacm32.dll
shfolder.dll
That's it. I'm really kind of embarrassed.
For any who care, Cubic Explorer makes a great file manager in this environment as well
Can ImgBurn be made to run under WinPE?
My very simple test failed, and before I go to too much effort I thought it wise to see if it is even possible.