For example if I have a paragraph with a certain style applied, I should be able to override some properties individually such as italic, bold, underline, strikethrough. 
 

I come from the olden days of desktop publishing and this was a core feature of all professional-level software — separate paragraph and character style sheets.

I would love to see this everywhere in Figma, but I think an urgent need is within slides. Because in slides we are publishing actual content and it’s a pain to create separate styles for little changes like this. They are also brittle and can very easily be accidentally overridden when reformatting something.