I think that if your going to do any development on this, your going to want it on your desk with the PSU plugged into it. It's not going to be too practical looping the cables all the way around to the front - far more practical to be at the back.
So, leave headphone jack where it is, and move the DC and USB connections to the rear. I know there's no room for that, so move the sd card connections to either the front or the side/s.
As for the volume, its fine as it is, as long as it's indented slightly so it isn't changed as you put it in your bag or whatever (like the NDS)