Hello,
Someone suggested this idea awhile back and I think it would be an excellent feature to allow users to further customize Obsidian. The idea is simply to allow users to browse and install individual CSS snippets, as opposed to entire themes.
This would take away a lot of the time consuming work of modifying a themes CSS. There is already a CSS Snippet meta thread, but being able to browse these snippets from Obsidian would be much more organized and I think encourage even further development from the community.