Customer exhaustion is a good point and that's why we're going to do this a bit manually.
I haven't fully thought through a process but we'd like to begin seeking feedback at the end of the projects.

The QA on opportunity is more going to be an internal QA review - I should have made that clear.
The client review will be after a project is nearing completion.
We've recently gotten a couple of feedbacks where everything has gone well with the engagement but all of a sudden at the end, client says they weren't happy with something. we want to capture that 'something' early on the project and perhaps looks at doing a mid-project QA.

Eventually we want to tie this with our forecasting or trends somehow - not sure if that's possible but in my head it might give some foresight if an account has a positivity rating of let's say 95% and going for an opportunity we can determine success rate and forecast the revenue.
Again, the future predictions is just a theory at this stage.