Good news, the Complete 4-String Cigar Box Guitar Book is now available. I've put many hours into assembling a book with thousands of chords on the 4- string tuned GDGB. I think I counted over 2400 hundred chord shapes! I'm sure there are still more, but likely all you will ever need.
I categorized the chords into the twelve notes in music - A to G#(Ab), then took the most common chord syntaxes. The syntax is not something you pay the government :). Syntaxes are the type of chords like major, minor, dominant 7th, etc.
Here's the cover created by my good friend Anton Pickard (thanks Tony):
Now you can approach any stye of music and find the right chords. Some chords are a bit weird and hard to finger, but there are at least 6 to 12 voicings of each chord so you should be able to find a usable shape. I hope you find the book an excellent resource for mastering the CBG.