Would be great to have a way of adding incremental values to properties in a character style.

In other words instead of setting a character style that has +20 tracking and is 9pt on 12pt leading, you would be able to set it so it is ++20 tracking (whatever the paragraph tracking is plus 20) and --1pt size (whatever the paragraph font size is minus 1pt) on --2pt leading (whatever the paragraph leading is minus 1pt) .

Percentages would also be great and even better if we can reference other properties (ie leading is 130% of font size).

Usage cases:
I often have to deal with Chinese text placed inline in English copy. This usually looks awful at the same font size, and usually the Chinese looks better either 1 or 2 pts smaller than the Latin font. Having the ability to make Chinese 1pt smaller than the English saves on stylesheets.

I also have to design stylesheets for Subs to use in InCopy on Headlines to fit them. Currently the 5 or 6 different headlines all have different tracking values and there is no way to create a universal "Reduce the tracking 5/1000em" and/or "Reduce the tracking 10/1000em". This leads to inevitable mistakes and ugly tracking.