I like this idea. There are some strange design choices on the Radial product... the proprietary footswitches could be replaced by MIDI or standard footswitch control, the low impedance pedalboard run could be done on a single multi-pin cable (5 pin XLR would be fine - easy enough to get hold of the cables), you could happily lose the extra #3 and #4 amp outputs, and it needs to be NOT YELLOW! An effects loop per amp, or at least a couple of switchable loops, could be implemented with TRS to save space. There also needs to be a loop before the buffered pedalboard run so you can patch in a MEG or similar to run those awkward fuzz pedals etc that don't work after a buffer.
So, 1U rack unit, 4 way input selector with a front panel override jack, pre-buffer loop on the rear panel, front panel 5 pin XLR jack for low-impedance pedalboard run, with breakout box (standard RJM Mini enclosure would be fine - could have a 6 pin XLR MIDI passthru potentially too, to keep things neat). 4 switchable amp outputs, either with independent loops or at least a couple of switchable loops. Tuner mute, switchable via MIDI CC (the ability to route a 2nd signal jack to the tuner out when it's not in use for the main signal would be a boon for guitar techs). MIDI control. Maybe a DI box selectable per input, for acoustic (this isn't a feature I'd be particularly worried about). RJM silver. Call it something like "Matrix Gizmo". Sound good?
Oh, and less than $1000. The JX44 is cool, but overpriced (as is all Radial stuff)