Yes you are right the document will take longer to print. I was able to type in 800 dpi even though the dropdown said only up to 600dpi and I think that helped a bit at the font size of 12pt. I got no warning. So you may still be able to over ride it.
If you're going 4pt font size I would see if I could print to a higher resolution laser printer or maybe even an inkjet. Even arial would not look great that small on most regular office lazer printers.
I will mention that out of those font.
Cambria -Regular works
Calibri - Italic works