I'd vote for #3. Glass centered in front of you where you'll use it most. Radios centered on the panel so easy reach from either seat. I would still put the radios on the bottom, as you don't look at them as often and looking farther down into the cockpit for less-used items is better user-interface design. This also leaves equal space on the right side for a second screen upgrade at a later date. Cut the hole for it to match the left-side screen, and cover with a matching panel... It'll save you the effort later. If you have the panel laser- or water-jet-cut, you can keep the cutout pieces and flush-mount one to keep the panel as clean as possible until you're ready for the second screen. Keep the second one to allow you to experiment with that space... Mount a tablet, camera, map compartment, etc. to the second one and you can remove it by swapping it for the blank insert.
I'd go one step further, and make a full radio "stack" in the center, to allow for future upgrades. Mount the steam gauges between standard radio width mounting rails, and even better mount them on a removable panel that mounts to the standard radio-width mounting rails. Then you can remove them and change that piece of the panel without re-cutting an entire new panel.
As for the necessity of steam: I'd suggest putting a Garmin 660 in there instead. The GPS altitude and airspeed will be good enough for any situation where your main glass completely fails, and the internal battery on the 660 will last until you're on the ground. When you're not in emergency mode, you'll have backup map, HSI, autopilot source, etc. as well.