This is really cool idea. Thanks for proposing it.
I think something like this could be more attractive to the founding member if it’s set up as its project from the very beginning (maybe via a yVCvault funded initiative?). This way the goal would always be to end up with an independent organization, which would provide strong incentives for the founding team. Initially this person (team) could work as part of the yEarn team and only audit yEarn contracts, but once the team has some experience and there is demand for their work outside of yEarn, they could smoothly transition to become a separate DAO.
As to the approach followed to train new auditors, I would leave that to samczsun, but personally learning by doing sounds like a good idea as I 100% agree that traditional ways of education and collaboration are obsolete.