What I'm proposing is to convince the same people that currently take care of the reviewing and selection process for an established journal to do the same thing for an open and independent variant of the same journal, which is run alongside the original journal.
Sadly these people are replaceable, and to my understanding the rights to the journals themselves are owned by the academic publishing industry. People don't really care who runs Nature; it is the reputation of the name that counts.
That's a good point, editors and reviewers come and go. Ideally, the newcomers would by default also be attached to "Independent Open Nature", until it becomes irrational to submit to Nature itself.
Am I mistaken?