Description
By supplying the special value of EMPTY for the createNodeSet parameter (via .../solr/admin/collections?action=CREATE&createNodeSet=EMPTY&name=myCollection&...) a collection can be created in the usual manner but it will just not yet contain any cores for any of its shards. Later on .../solr/admin/collections?wt=json&action=ADDREPLICA&collection=myCollection&... calls can create cores as and when and where required.
github pull request with proposed changes to follow.