This first revision has been done in a bit of a hurry inspired by the opamp challenge. It's the minimum viable product & uses a couple of small DC-DC converter modules. But even this will be a very welcome downsizing from what I've been using before it.

For the second version, I am planning to integrate ... 

• my own DC-DC converters & USB LiPo charger etc.
• a headphone amplifier
• individual switches for XLR shield ground/float
• individual switches for phantom power: 48V, 24V, 12V, 5V, none.
• individual switches for muting an input channel
• switches on the /2 inputs to bring the level back up to the same as the /1 inputs*

The last item would allow it to also be used as a 2x stereo (+1 mono) mixer.