I have a few questions:
(1) Are the cable-routing channels blocked when you install an E-ATX motherboard?
(2) Are there any E-ATX compatible cases that have cable-routing channels that are not blocked by an E-ATX motherboard?
(3) With cases that have side panel fans, what happens if you forget to disconnect the fans before removing the side panel? I imagine your motherboard will get a hard tug, and perhaps some bent pins. Are there such a thing as a safety quick disconnect fan cable extender? I.e., a fan cable extender that is designed to be the weakest point, so that if you tug it, the cable extender will disconnect, without putting tension on the fan or the motherboard? If such a cable exists, then removing the side panel without first disconnecting the fan might break the cable extender, but that's better than breaking your fan or breaking your motherboard.
And a comment:
I would have liked to see bottom fan slots. In my current build, with a Supermicro M12SWA-TF motherboard and a NH-U14S TR4-SP3 cooler, the heatsink is oriented so that the CPU fans blow vertically. So in my Phanteks Enthoo Pro 2 case, I set up the case fans so that I've got 2 exhaust fans directly above the CPU, and 2 intake fans at the bottom of the case, blowing upwards towards those 2 exhaust fans. Those 2 bottom intake fans are probably not essential, since I also have 2 front intake fans, but I like having them anyway.