When searching something via Spotlight on Mac it correctly opens Orion but it uses the default search engine from Safari and not Orions default (like Kagi).
My suggestion would be adding a similar redirect feature like the one used in th Kagi Extension for Safari, where all requests to a specified search engine (or all) are redirected to Kagi.
By adding this feature, the spotlight search becomes usable to users that don't use one of the by apple provided default search engines.
For me the focus lies on Kagi, but I don't see why you couldn't provide the possibility to redirect to all sorts of search engines later on.