Actually, if we want to nitpick, The ARNOLD SW1200 came out the same year as the Life-Like SW1200. This engine featured the old Riv hood but with a new metal walkway, thin handrails, detailed fuel tank and S2 style drive train. The ARR-A trucks were swapable with the S2, which is what I did for my S4.
Want my nutty theory? Atlas is taking their sweet time on the S-series for several reasons:
1. They would require a new motor over their current engines.
....This is now solved by their MP15/Machima motor.
2. Weight is a serious problem when making it DCC
....New smaller decoders would be able to sit in the cab or fueltank.
3. They want to release all S series from S1-S4
4. The chassis would also work for an SW1500 due to a similar hood with and truck spacing.
