Michael, if you can create a lever harp with all the advantages of the pedal harp – especially with regard to weight and cost, I will hero-worship you! Go for it, I say!
Have you heard Catriona McKay’s music? She developed a harp in conjunction with Starfish harps in Scotland which has a chromatic octave below middle C, and the rest of the harp is diatonic. It is a compromise, but allowed her to do much more chromatic stuff than a standard lever harp. Check out her website http://web.mac.com/catrionamckay
Or her Myspace site – search for Catriona McKay in the music section.
Enjoy!