I have tried with Map integrated in Lightroom (Google), Geonames with Imatch and OpenStreetMap as LR plugin. None provides the same result or satisfactorily solves (...)
Different geo-coding services have different purposes.
Google is mostly interested in monetizing things by marketing and hence lacks in
off-road terrain.
OpenStreetMap and GeoNames.org are volunteer-driven projects and usually have more detailed maps for off-road terrain, bikers and hikers. If not, you can add your locations to improve these systems for everybody.
HERE is owned by the automotive industry in Germany and focuses on highly-detailed and up-to-date street maps.
If the precision of all these services are not sufficiently good for your requirements, using IMatch locations (if you often geo-code the same place) or doing it manually or copying it from a 'master' image are good work-arounds.
I'm not adverse to the idea of setting up a complex system of inter-related tags as suggested in this FR (this comes up once or twice every year), or something resembling the powerful
keyword links in the IMatch thesaurus (were assigning one keyword can assign 5, 20 or 50 other keywords). I have pondered this several times, but was always unsure if this would really be needed...
I wonder how many users will ever use this. If you have only 10, 20 or 30 cities, IMatch locations ("Frankfurt") or metadata templates (if you also need to fill non-location tags) or a combination of both (metadata template which assigns a location and also fills metadata tags) will do the job nicely.
And they are available already, today.
You can assign favorites to these templates to apply them with a single click or keyboard shortcut.
You can even combine multiple of your metadata templates in an
Automation Favorite to apply them all at once, and do other things as well.
if you take photos at the same locations often, use locations.
If you take photos at a spot only once (e.g, vacation) select all files and fill in the data once in the Metadata Panel.