I think the addition of lead sheets would be a great idea! Though, being lead sheets, I'd feel obligated to offer our content in the four most-requested transpositions (Bass clef, C, Bb, and Eb), in which case it would require more from the arranger(or should I say, purely 'transcriber', at this point)
Personally, I don't see a problem with expanding our library to any sort of instrumentation, just as long as we have quality content to offer and can find a logical way of organizing it.