You'll want to get down to millimeter.
For one reason...There are already tons of public LIDAR datasets with point data down to millimeter.
I've even seen monuments and public art sculptures that have LIDAR datasets down to millimeter precision using WGS84 base references. (think knowing the coordinates for George Washington's left nostril on Mount Rushmore against trilateration references of WGS84 ... crazy I know, but its out there)
Having it all queryable in Wikidata ? hmmm... not for me, other data catalogs and GIS systems handle that job.
But having the datasets linked etc. to spatial references ? You'll want to ensure that folks can populate against a spatial reference property like the City of Georgetown example link above that gives: