Ok, a couple of things. First, a glance at my panel in this
thread to show you where I'm coming from.
Now, will you be using the 496 regularly? If it's a backup, then I'd set up a mount that places it over one of the displays when needed. Then I'd use the side space for your backup instruments.
Ergonomically, I'm not a fan of having the switches up high. I like them low and close to my hands. If you intend to have a copilot, centering them would be a good idea. Not so important with the CBs, as they shouldn't get used much. By the way, there's a pretty good CB/fuse debate going on; I think Stein had the best things to say in there. Worth looking at.
I'm not familiar with your EFIS of choice. I only need one display for mine and the picture you have shows a similar display mode: HSI and moving map. Mine has a synthetic vision window above the HSI and I can call up the engine display with a single button press; press again and it is dismissed. I also get a pop-up window to run the autopilot. I'm not trying to sell you on the BMA EFIS; I'm leading up to the thought that you may not need a seperate autopilot head or a second display. A little research into the capabilities of your EFIS would clarify that for you.
My panel ended up with a lot more 'stuff' on it than I had originally considered. Above the start switch are the switches for the autopilot master and the backup battery for the ADI. Below the compass, along with the hobbs is a CO detector and the remote panel for the ELT. Above the glove box is the fuel injection purge control and the switch and breaker for the battery backup to the Lightspeeds. To the right of the glove box is a music input an mute enable switch, plus a power receptacle. And I was determined to keep the tip-up canopy release, so room had to be allocated for that. It took a few iterations before the layout was finalized, so be prepared and be flexible.
Finally, consider putting the headset jacks on the seat brace between the seats. Having the cords behind you is better than in your lap. It also frees up a bit of precious panel space.