Improve OSM external data usability in Kartographer
Problem: It's possible to highlight boundaries, routes etc. in Kartographer using external data from OSM. However current external data support has a couple considerable deficiencies. External data reference (Wikidata id) in mapframe syntax may return nothing, resulting in a blank map instead of auto-positioned object when there's no Wikidata tag on OSM or no OSM object available or when reference becomes outdated (OSM generally stores only current objects). So it's hard to use this data reliably and conveniently in infobox templates. Secondly, certain type of geographical objects are not available for Kartographer (most notably waterway relations). Thirdly, Wikimedia currently generalizes OSM external data in a quite unfit way (most notably for large boundaries and long routes).
Who would benefit: Wikimedia projects, mainly Wikipedias that have articles about related geographical objects.
Proposed solution: 1) Provide way to check if external data reference returns external data, 2) handle OSM relations at least as well as WIWOSM (older service, largely unmaintained), 3) rework data generalization.