I like the design with the front I/O at the bottom vs. having it on the top. Though, I wonder what that'll do for cable management. With the radiator on the bottom, those cables need to be able to head directly up and out of the radiator area very close to the front of the case. That might influence how/where you mount the cabling for the I/O and power switch and could make that really tight. That being said...I like the external look a LOT.
Side-mounted, those cables are already in the upper section and can be easily run to the left side of the case, along the back and plug into the motherboard headers without too much difficulty or getting in the way of anything.
It's probably a simple enough thing to work through. Most of the I/O cables are easily bent and twisted into whatever shape you need. I'd mostly be worried about the USB3 header, which is generally really bulky and difficult to deal with vs. the rest of the cables.