What I have in mind is to use 2 of Dave's Boards (or something based on his design) but keep them isolated and floating so that they could be connected in Series for grater voltage or a -V_0_V+ Supply or paralleled for a larger current output. They would have to be in close tolerance but I think Dave's design has taken that into account. I would leave the MCU on the board for the sake of reading the Encoder and driving isolated communications via SPI or TTL Serial, but not worry to much about adding any advanced functions to it. Possibly not even a display at this stage as you could use a DMM to set the Current limit and Measure the Output Voltage.
Later I would add a separate control board, with a larger processor, to take over the display and control input functions, with software to add tracking and other optional capability's such as computer control, voltage sweeps, stepped patterns etc. for bench testing of devices.
As part of the CPU board I would include a relay control to automatically configure the outputs into Independent / Serial tracking / Parallel Tracking configurations. Because it has to be isolated from the 2 power channels and independently powered it could also provide fixed outputs of 3V3. 5V and possibly 9/12V if it is driving relays. thus providing additional common supply voltages and freeing up the 2 main channels for more productive tasks.
If i were to change the current design at all it would be to simplify it rather than add features.
Even with only 10bit resolution on ADC and DAC you could control 0->1024mA in steps of 1mA and 0->20.48V in steps of 20mV, which I think would be more than adequate for most hobby bench supplies and indeed exceed the measurement capability's of most hobbyist DMM's, so I would be inclined to use PWM and on chip ADC of the MCU rather than increase the cost and complexity with the external devices. For the same reason I would argue that the inclusion of the uCurrent is also an unnecessary expense. If I were designing something that had low voltage and current requirements, such as MCU devices that draw down to the uA range in sleep mode and nA normally, I would not be wasting 10's of watts of power by testing them on a bench PSU like this one. For those applications a precision PSU of 0->6V @ 0->10mA with very fine resolution would be a good investment.