@dy3p Been waiting for someone to post an experience like that. Visitor (600) to 457, yes, because that's what happened to me.
Since there seems to be no restriction about lodging a PR visa (186, 189, 190) onshore, nor expressed conditions on Visitor visa holders not to lodge a permanent visa while onshore, I think it is possible. I have read some posts that prospective marriage visas need that the applicant be outside Au at the time of grant, as such informs applicants who are onshore to exit.
Also, when I was on visitor visa and applied for 457 while onshore, a BVA without work rights was issued, but I was able to request work rights by applying and submitting proof of financial hardship. I guess, the same can happen to a visitor visa holder applying for PR visa onshore.
Just to be clear, this is not dogma... just sharing my thoughts.