Recently, I have added more rigor to my personal guitar chord library with the addition of inversions. I developed the "drop 2", "drop 3", and "drop 2 and 4" voicings for all seventh chords.
For ninth chords, the typical convention appears to advocate rootless "drop 2" chords (using the upper voices). While I recognize that this approaches complements a bass player in a band context, it just doesn't strike me as the "right" way forward for me.
So, what other techniques do you recommend for developing voicings for ninth (and higher) guitar chords, where the unaltered fifth is commonly omitted? (My present library dwells on the root-in-the-bass chords, while keeping the extension voices in the proper relation to the root.)