Please make a request at this Github ticket. Full genome request instructions are included the top post: https://github.com/galaxyproject/galaxy/issues/1470
Updates are not planned for the very near-term and the source will need review. Non-draft genome builds from public sources like NCBI, UCSC, Emsembl, etc. are preferred.
For immediate use now, the Custom Genome/Build function can be used. How-to: https://wiki.galaxyproject.org/Support#Custom_reference_genome
Best, Jen, Galaxy team