Voltronic, the variant I've been long dreaming of is a straight 6 or 8ch 24/48khz PCM recorder in a candy tin. Single common 9-pin DSUB input connector to accommodate 8 unbalanced mic channels > low voltage mic power > gain trims > write stereo WAV(s) to SD card. The On/off switch providing operational control - switch it on and it records, switch it off and it stops. Small and simple. I'll do the mixing later.
I didn't really see this post until now. Wow, this sounds like an outstanding idea, sort of a DPA d:vice on steroids and not requiring an external control / recording device.
As long as the preamps have low noise such that you can set the initial gain low enough not not require any limiting, this could definitely work. Maybe have 3 fixed gain levels, such as what Jon had on the Littlebox / Tinybox - no need to worry about channel linking since all 2/4/6/8 channels would be fixed at those switched levels. That would also make it useful for Soundfield or similar applications.
Such a device wouldn't even need a display if it's a one or two switch operation. Maybe just a few cheap LEDs to indicate power, signal presence, or error. Card formatting and similar operations would be handled on the user's PC as it should be.
The only thing I'd possibly change to what you propose would be to have it write a poly WAV rather than separate stereo WAVs, such as what you see in the new SD MixPre line. Writing one file at a time is likely to be more reliable than writing 3 or 4 simultaneously. You could make it such that all 8 channels are recording no matter what, or arm/disarm using internal DIP switches.
The closest thing to this that actually exists might be the
Sonosax miniR82, but the device you're proposing could be much simpler (and much cheaper).
Someone needs to build this thing!