No, it wouldn't. Can't test easily, no easy change out, no reproducibility..
See below
Why do you want to throw away the baby with the bath water? You still don't get it. It is not just about building a very large rocket. It is about cost.
I didn't say throw it away--Ship 5 with the single downcomer would be sufficient for an expendable Starship anyway. An expendable design would cost less--be less of a headache though.
Perhaps lunar Starship could use a single downcomer and accumulators both to be extra safe. It could land then.
In the past, I championed the idea of "rocket-as-payload" with wet workshops.
Now it is "rocket as engine."
Your criticism about such a design (can't test easily, no easy change out, etc.) could just as easily apply to NASP, where the whole vehicle is an inlet.
Since Starship is designed for re-use--and since the stock Starship is designed to be recoved via chopsticks catching it just below the forward fins --you don't have to worry about landing it on the bottom--so the whole width of Starship's tail could be a super-wide nozzle.
Remember the concept where you had three SRBs connected by struts?
Have those reach up instead--attached to the sides of Starship just above the engine.
This gives more separation between the two stages. Instead of a hot-staging ring--just have curved panels that bear no real weight that blow apart at staging.
If NASP could have been all inlet--perhaps Starship can be the all-rocket equivalent of that--with injectors being all that needs changing out.
Having the whole lower part of Starship be a beefy nozzle lends itself to re-use.
That part can be swapped out if need be. They can take hot stage rings off, after all.
In the CSI STARBASE video, aluminum was called for on some lines.
At the New Materials thread, I posted a link to a phys.org article about aluminum that had better strength when cold.
Even if Elon doesn't want an all aluminum bird--he could at least use that for propellant lines.
On the subject of propellant lines if might be good to have as much plumbing being outside the rocket for EVA/refueling --and to limit leaking propellants into confined areas where you could have an explosion.
With as much plumbing on the exterior of the rocket that you can get away with--leaked propellants just goes into the vacuum. Tesla valve fuel lines may limit Pogo as well.
