I have few work copies from the 80's, A1 maybe and I'd say that you do not want those, if not now then eventually.
It's like an effect decoration, it must really mean something or it becomes old, fast.
A2 is close to 50x70 poster, it's target audience is few meters away and effective time very short.
Old maps are a good opposite.
I'd pick something elegant and simple or something that is still unknown after few looks.
Should it be a single page or is mosaic allowed?
Dot per inch is not lines per inch, RoGeorge's example is a good one.
Black and white scan has its down sides but it's still clearly hand made.
If you then want those white spots inside black filled you must drop dpi.
But 300 dpi is much and gray scale doesn't need much.