Many of the stylistic duplicates, for example the half-width and full-width latin forms that you mentioned, are only in Unicode because of backwards compatibility with pre-Unicode character sets. If there hadn't been character sets that had different encodings for half- and full-width forms, Unicode never would have had them either. So you can't use them to argue for more glyph variations in Unicode. The same applies to many of the formatted numbers, such as the Unicode characters "VII" (U+2166), "7." (U+248E), "(7)" (U+247A), and "1/7" (U+2150), and units of measure ("cm^2", U+33A0).
(Oh, for Unicode support in Slashdot....)