Currently, when you select a vector group with too many layers it has a huge amount of fill and gradients. This is applied to illustrations from stock. For example, a basic illustration can include more than 200 various colors. It would be great if there will be an option to simplify these colors to a certain number (for example, 10 colors). This way you will save a lot of time rather than going through 200 colors one by one when you need to change the color schema.
That sounds like a great case for a plugin. There already is a plugin with similar functionality: Match fills to local styles. Maybe send this suggestion to the author of this plugin, they could improve it or make a new one based on that? Or you can use it for your use-case already.