Actually with the historical performing practices, many orchestras are experimenting with alternate pitches - but NEVER with the same instruments. The lower pitch normally comes with gut strings and period instruments or copies. A violinist playing at 415 has as much trouble as we do playing a natural trumpet. The woodwinds cannot be tuned over great differences. The holes have to be aligned for the frequencies and 415 means a lot wider spacing. So, even if the heavyweight comes in, no 432 unless the orchestra has instruments for that pitch and the rehearsal time to fine tune the ears of all involved in the project. What you guys are incorrectly assuming is that all of those lower pitches were originally "well-tempered". A lot of other things happen in ensembles that play at lower pitches. Sometimes we play scales and chords to get fine tune the mean tone ears.