Something I'm looking at is making the 3xHDD internal bay hot-swappable. Corsair does something like this for their 900D case by means of a makeshift backplane. Link
It would be a welcome addition because: When I'm building a computer I want to account for all the hard drives that could possibly go into it from the beginning and accommodate that with the # of SATA ports on the motherboard or even planning for a HBA.
If I want to put in another hard drive and I don't have external hot-swap, I'm ok opening the side of the case to put a hard drive in but I certainly don't want to have to open the back and route wires.
+1 on the slim ODD for the 915, but can you clarify whether that would remove the I/O panel entirely?
FYI these are both things I'm working on right now for my HAF XB build - designing and 3D printing a 5.25 bay --> Slim ODD + hard drives (Either single 3.5 or 1-2 SSD)
Making the 4x2.5" bay hotswappable. I put this on hold because I already got 2x 1TB velociraptors so I hope not to need to switch them out often (preferably at all) and I don't feel like dealing with PCB design right now, but with SATA extension cables and a 3D printed housing that clips to the back of the rack, sure.