I’d look at it as a nicer sounding 302 with more functionality (direct outs and AES3), rather than any kind of alternative to the 688. I’ve still got mine- it sounds lovely still, but the R4+ preamps are up a notch on these I’d say
The SX-M2D2 looks like it’s pretty much exactly what you’re after (it’s also *tiny*), but still in development and I doubt it’ll be available before the end of the year. I’ve attached some photos of the prototype casing, but it may well change (they were looking at changing the controls and putting them on the shorter side)