Why would we (as in wider OSM) want websites etc that are not under control of the OSMF but are run by independent hedgehogs look like osm.org? It is bad enough with the widespread use of OSM in product/site names causing confusion, I don’t think we want to make that worse.
And the Wikimedia situation is -very- different, they run numerous different projects with at least a dozen websites and a formal system for a common look and feel makes sense there.
That’s why, while I applaud Gustovaos engagement, the whole reusable and formal bit of the project seems a bit misguided, and IMHO would be better spent on simply improving the usability of osm.org (OK a better working OSMF website theme could be a good idea, but that has always been considered non-core).