Have you considered something like this for the back plate to clean it up a bit:
so drill out the rivets circled in red from the current IO and then make your own panel that incorporates holes (green) for the Scythe fan controller and then just remove the current front plate from it and a hole where the current hole is where you were going to put a switch. you could then just rivet the central section of the current back panel to the new one? I would also use much smaller bolts to hold it on (countersunk?)
Just my opinion as it does look a little messy back there, sorry!
shouldn't cost you much, just patience and the cost of the sheet of metal if you dont have any already! As I said just my 2c