I mostly agree with that but at a minimum it has to be 3, with 4 being ideal. The last 8 seasons we have used 2.5 QBs on average. We shouldn't be forced to do what we did last year, TE and Wildcat. Also you need guys to run practice with. If QB1 goes down do you want QB2 to be your starter and have to run scout?
Last year didn't matter because Dino was let go, but if that were to happen this year the story would be a lot different. Sure in terms of Ws and Ls it won't. But in terms of development and learning the O, it would hurt going forward. Once QB1 goes down the rest of the season is a practice for the next season. So we want to actually be running our base O, even if it doesn't do a thing with Ws.
Like you said, a quality QB isn't going to stay long term and wait it out. But we can still get kids like Lamson or Morgan as bodies for 1-2 years as a break in case of emergency QB with no plan to have them ever be QB1. And who knows maybe you get lucky and find a diamond.
So IMO we need one of CDRW or Davis to stay. That will give us 4 QBs with Williams and the preferred walk on coming in. If both leave we should be looking to bring in another body.