Hello Affinity!
I'm pretty sure you are figuring out a way to update symbols to follow more modern standards you see in development of UI, but has a great benefit to any artists & designer as well; Symbol Variants
Much like modern design systems, you would like to sync how you work in design & code, so you don't have two ways of doing the same thing. Figma recently released Variants and it's exactly what you would like from any modern tooling for designers that need to get their product shipped faster; https://help.figma.com/hc/en-us/articles/360056440594-Create-and-use-variants
Second, I'm confident they are working on such a feature or redesigning how that works from the ground up. But Affinity has so many advantages over any other software I've used for vector graphics editing, that I can't say how much I would use it for my daily desingn work over anything else like Figma. But for that I really need symbol variants, and I feel safe to say "we".