footway=* instead of sidewalk=* on roads

[Famlam]

​The key footway is quite often incorrectly used when (in most cases, most likely) sidewalk=* is meant.

Perhaps it is an idea to make the validator complain about "disallowed" highway values combined with footway=*? (Formally it's allowed on highway=footway/path/construction only, although it seems quite a common tag to use on highway=cycleway too)
​overpass-turbo for the area around The Netherlands

If not, then it might be worth adding a check for footway=* without highway=* tag (or prefixed highway keys)? ​Overpass-turbo

/* 19603 */
way[footway][highway][footway=sidewalk][highway!=footway][highway!=path][highway!=construction][highway!=cycleway] {
  throwWarning: tr("{0} together with {1}", "{0.tag}", "{1.tag}");
  group: tr("suspicious tag combination");
  suggestAlternative: "sidewalk=left";
  suggestAlternative: "sidewalk=right";
  suggestAlternative: "sidewalk=both";
}
/* 19603 */
way[footway][highway][footway!=sidewalk][highway!=footway][highway!=path][highway!=construction][highway!=cycleway]
  throwWarning: tr("{0} together with {1}", "{0.tag}", "{1.tag}");
  group: tr("suspicious tag combination");
}

/* 19603 */
way[footway][!highway][!/:highway$/],
way[cycleway][!highway][!/:highway$/] {
  throwWarning: tr("{0} without {1}", "{0.key}", "{1.key}");
  set MissingKeyWarning;
  group: tr("missing tag");
}