I thought that rendering a font at say 8pt and scaling x2, is not quite the same as rendering a font at 16pt.
"In the age of metal type, character design and spacing were adjusted for the point size of the font. Smaller size fonts typically had proportionally wider spacing, heavier stems and serifs, and less contrast between thick and thin strokes than larger size fonts." (http://www.prepressure.com/fonts/multiple01.htm, third bullet point, half way through the page).
A font technology that allows such variations to be requested on a continuous scale is "multiple master" fonts. Adobe's multiple master format is dying away (not really supported in MacOS X, Adobe isn't making any new MM fonts, though continues to use them in its products).
That page also notes that Adobe Illustrator 7 and later have "direct built-in support for MM fonts, allowing you to modify MM fonts using a simple slider."
pjrm.