I get to have a down under (looking up) view of DT for various Atmel SoCs: at91sam9g20, g25 and the sama5d3. Forget auto-detect of macrocells: there are so many (I just counted 38 on the sama5d3 and that is without instances, so I counted 1 for the PIO but there are 5 instances), that they can't all be configured. At least two reasons: the 160 gpio pins would be insufficient to route them to the outside of the chip, and the power budget for the chip would probably get blown (literally). The main way that SoCs save power is by _not_ configuring macrocells (or configure them at lower clock frequencies). So again auto-detect is just wrong for SoCs.
Well yes, DT is a replacement for the kernel command line which obviously can't handle the amount of data we are talking about here. And having a specific DT blob boot the same SoC on another OS is a nice idea, I'd put that in the same category as nuclear fusion for large scale electricity generation :-)