Here is my feedback to two of your points:
1. Totally acknowledge the 3-6 month ramp up time for a product, but engineers can easily take that long to be productive and fluent around the technology stack, so I would argue that unless you are hiring a domain specialist, a generalist of any sort will take that time and be a risk for around that long.
2. I acknowledge your PS and I intentionally did not this post a huge backstory because that is what an interview is for, and the point I was making by asking this question was how to even get to that point.
3. As another poster indicated (and as I am aware since I’ve been working for awhile now); obviously it’s easier to make a non-standard transition in your current organization, but it isn’t possible if your org/team doesn’t hire for these roles or if you’ve joined a team where there is already someone entrenched in that role. So in that regard, I believe going across-orgs is probably an easier move, and appreciate everyone’s advice in that direction.