Cool idea, Drew.
But that's not really too far from what I do.
With the bottom 3 strings tuned in 5ths, I get the extended range (who needs 8 strings? I'm already at Gb/F#) plus the simplicity and familiarity of the top strings being tuned standard.
I think of this tuning in an almost jazz respect. My bottom 3 strings are bass, my top 3 strings are chords and melody, and the d string in the middle is the intermediary between the two, used for both bass lines, riffs, chord structure, and lead lines.
With an 8 string, I'd have one more, which would be a low Cb (enharmonic here. Keeping the logic of the tuning. B 1 octave below the standard 7-string B for you perfectionists.) But I don't really see much need for this. This note is to my mind solidly in the bass guitar register.