I would remove the IC4A buffer.. I would use it for buffering the Vref..
Otherwise the Q is how stable with different loads and fast the CC CV loop will be.
I was curious as to why there was a buffer and my only thought was to use up that opamp so its not floating. I am not sure about what you are talking about with the Q and stability. As for putting the buffer on the Vref I would think (zero formal experience) that the less things you have in your VRef the better, as each component has its own temp co and drift.
Daves circuit is a really poor starting point for a lab supply. Usually starting with a voltage regulator is a poor idea, as is it hard to add a variable current limit. The poor starting point was a reason the µ-supply never got finished because of problems under certain loads.
My best advice on this circuit is try to find the the errors and weak point and learn from it, but do not try to fix it, as it's starting with the wrong concept. It's easier to start from scratch.
A much better starting point would be circuit from the start of this thread:
https://www.eevblog.com/forum/beginners/0-30v-0-3a-psu-audiogurus-version/msg2232978/#msg2232978
The task would be to get around the the negative supply. A simple way would be with 2 powerful series diodes to generate some -1.2 V. Not very power saving but with some 19 V to start with and a 12 V target the voltage is there to spare.
Something like 0-14 V at up to some 2 A should be relatively simple
However there is a downside of using a low side shunt: it is hard to add a second output. So the fixed 3.3 V and 5 V would need a different power source or fully isolated with a switched mode converter.
I was initially thinking about doing something without using a regulator, but decided on using a regulator to expedite the process. It will be interesting as I go through this process what I learn. In the end I will most likely build something else for my true bench power supply as this will not fill all of my needs (I want multi channel, and much better regulation, and measurement)
Is there anything that is going to be disastrous with this design, or will it just have quirks that I can analyze and learn from as I build and test it?
In reality the projects that this will be used on will all be low current, and I foresee using the fixed regulators more than the CC/CV. My interest is in PIC, FPGA and possibly some RF stuff (I am a HAM after all) I could cover 99% of my use cases with 150ma fixed supplies in 5V, 3V3, 2V5, 1V8, 1V2, -5V. I do plan on adding the 2V5, 1V8 and 1V2 fixed supplies to this project before its finished. The CC/CV Adj is more of just something to play with as well. If you notice I also am sending all of the unused IO to a header and have lots of LED's to play around with, so it will also be a dev board.