I'm not too sure how to explain this, or whether it can be achieved but here we go.
1) Create A3 canvas which acts as a visual. It has a scaled print artwork in the middle, with dimensions round it and a code. On the A3 you can add annotations etc and export the A3 as a visual to present.
2) With a ready to go A3 booklet with various pages all of which have a print ready artwork in the middle. The ability to export this artwork in the middle as a High res PDF without the A3 space around it but all from the same file so nothing has to change. (Except maybe relinking high-res imagery)
3) The print ready artwork may have a few layers. For example a layer for the logo (locked) so it cant be changed, and a code layer with a unique code on it (locked) so it can't be changed. Is there a way to take this code and make it become the page title and link straight to a contents page?
So in a nutshell, creating a indd template that works initially as a visual for proofing but can then be exported as a high res PDF. So for future use, images can be updated but dimensions, logos and codes remain as per the original.
Hope that makes sense.
You could define a huge bleed area and put all the annotations etc in there, then set it as normal (3mm?) when you export the print-ready PDF.
But... Personally, I think I'd prepare the whole booklet as one document, properly formatted at final page size with facing pages in logical order, then create a new document, import the original INDD document into it, add all the annotation etc and call that '[filename] PROOF' or something like that.
Placed indesigns within an indesign template, locked with captions that run to contents page. This allows instant update of visuals and 'edit original' for safe editing of final artworks using locked layers.