Don't know if you'd be interested, but I've lately tried the Lee Oskar harps in minor keys, both natural minor and harmonic minor. The natural minor is meant to be played in cross-harp as described above, but if you get, say an Bm (natural minor) harp it plays a lovely D dorian scale in straight harp position. The harmonic minor harp plays in the key printed on it, but it is a slightly different scale, said to be useful for eastern (really central) European, gypsy, and Jewish music. I love both kinds.

As for 12-strings, I have nothing to add except that the best sounding ones I've ever heard were Martin, and with their light construction they might be best tuned down a fret or two. Another great one is the old Gibson B-25 12-string, and Guilds are consistently good. I guess I would recommend today that, in general, the higher quality your instrument, the more likely it is to be safely tuned in standard pitch.

Good luck, Chet W.