I would consider that impractical to do because the accessories are not on the same plane. Not impossible but you'd have to do some serious pulley work. There would be no gain because the accessories would still create the same HP robbery by being connected to the same crank pulley. I guess you can make a case for less drag with one belt but the results would be marginal. The other downside is, if that belt breaks, you lose everything vs just the PS, AC or WP/Alt combination.