No one style can serve every purpose. Already the needs of Wikivoyage are pulling in different directions than a base layer for Wikipedia. A statement of the purpose of the style and goals would help identify what feature requests should be added and what should be rejected.
https://github.com/gravitystorm/openstreetmap-carto/blob/master/CARTOGRAPHY.md might help. Its purposes are quite different, but it gives an idea of what to outline
https://github.com/yohanboniface/OpenRiverboatMap#design-philosophy is another other sample design philosophy
enwiki has this good styling guide that might be the starting point for this task