My own suggestion would be for Atlas to put out a nice 40 to 50 foot steam-era mill gondola (Oh, where, Oh, where did the old Roco molds go? :-p ). Also, as colorful as the New York Central's Jade Green freight car scheme was, could Atlas please paint more of its steam-era freight cars in one or the other of the NYC's older schemes? For those like me building up a late Depression--early post-World War II freight car roster, the Jade Green scheme is too anachronistic.
I'm also hoping for an undec 2-rail RS-1 with DCC.