Microsoft provides some information on what features a word processor should support by default for certain scripts.
There are not many special complications in latin. Latin fonts can generally fit in a single byte encoding with no (or few) font tables. There are a plethora of accented glyphs which should be built. Kerning should be generated for some glyph combinations. A few ligatures need to be generated (the "f" ligatures: ff, fi, fl, ffi, ffl and perhaps st).
You may want to add a set of smallcaps. If you do, Adobe has reserved a block in the private use area for latin small-caps.
Some languages have specific requirements of their own
Greek also does not have many complications. Modern Greek fonts generally fit in a single byte encoding. There are a few accented glyphs that need to be built. Kerning should be generated. I am not aware of any standard ligatures for modern greek (ancient greek had ligatures and variants on some of the glyphs though).
Small caps are again an option, and I have reserved a block in the private use area for them.
Cyrillic fonts also fit in a single byte encoding. There are a few accented glyphs. Kerning should be generated. I am not aware of any standard ligatures.
I am not aware of any need for small caps (in most cyrillic fonts most lower case letters are already small caps).
Again some languages need different glyphs
Arabic needs a complete set of initial, medial, final and isolated forms -- Unicode has reserved space for these. Arabic also needs a vast set of ligatures -- Unicode has reserved space for many, but I'd guess that extra ligatures will be needed sometimes. Arabic also needs a set of mark (mark to base, mark to ligature) attachments to position vowels above letters. Arabic may need a glyph decomposition table.
I'm told that in good Arabic typography there need to be many more than 4 forms per glyph. I'm not sure how this should be supported.
Right to left.
Hebrew has a few final forms but no special tables are needed for these. Hebrew may need kerning. Hebrew should have a set of mark (mark to base) tables to position vowels over letters. Hebrew may need a glyph decomposition table. I am not aware of any needed ligatures.
Right to left
Indic scripts need a set of ligatures.
(they probably need a lot more but I'm not aware of what)
The Hangul script consists of a set of syllables built out of a phonetic alphabet. Generally fonts consist of a set of precomposed syllables.
Complications are introduced by the massive combinatorial explosion of all these syllables. These are eased in postscript by CID-keyed fonts.
Vertical writing and left to right writing are used, and some glyphs have a different orientation when drawn vertically (parentheses for example).
Again a massive collection of glyphs is needed, and postscript uses CID keyed fonts to deal with this.
Vertical writing and left to right writing are used, and some glyphs have a different orientation when drawn vertically (parentheses for example).