When using OSM Scout Server, you can achieve it manually by entering hierarchy split by comma (syntax described at the bottom of https://rinigus.github.io/osmscout-server/en/). Its far from what is proposed, but can be used. For other geocoders, I don't know if they support something similar.

Realistically, I don't expect it to be moving in this direction any time soon (nor in my understanding of the term, nor in soon^{TM}). I will have to work on geocoder, but there are "few" issues in front of it. Currently, working on Mapbox GL backend update. Managed to get latest version working but there is some performance issue which has to be tracked down.