Tuned in 5ths, that's what I was thinking of. As you say Twick, some dissonances are possible but I think it would hurt my brain too much to try and predict where they'd be.

Ideally I'd need a range of guitars, to avoid re-tuning between tunes: 6-string standard, 6-string DADGAD, 12-string standard, 12-string DADGAD,12-string tuned in 5ths... then an electric version of each of the above... Hmm, I'd need a van (and a grant from the Arts Council to fund the lot)