A few questions (and possibly feature suggestions?)
How is the indexing of geoshapes different from geo-points behind the scenes? is the geoshape not mapped to many geohashes as the geopoint is mapped to a single one?
Why is the geohash_grid aggregation applicable only for geopoints?
Similarly to the murmur3 hashing by adding an inner field in the mapping, why not allow for access to the geohash itself by the same means?