Fonts should be built more efficiently
Current version of Ume fonts contains too many identical glyphs between different font files. Ume Gothic/Mincho, Ume P Gothic/Mincho, Ume UI Gothic differ only in the glyphs covering non-CJK ideographs. With most space in each font file allocated to the CJK ideographs, duplicate them in each font file is a tremendous waste in storage space. Further possible wastes are also found with the use of C/S/O-fonts, whose only difference seems to be the dotted zero (see claim in Ticket #26715).
To cut down the tremendous bloat, all future fonts of same style and weight must be built in a font file format supporting multiple fonts in one single file and allow sharing resources between font, such as TrueType Collection (TTC). As for the dotted zero, they can be safely compacted using OpenType layout tables to allow users to choose between variants of the same characters in compliant applications. TTC and OpenType glyph substitutions are available in FontForge.