This is an interesting topic even though I no longer work with Java these days.
For rendering glyphs at large sizes, where texture atlases are not possible, it may be worth looking into paths rather than texture atlases. I have an offline node tool, fontpath, which I'm using to generate glyph paths. If FT_Outline_Decompose is added to FreeTypeFontGenerator, then you would be able to extract glyph outlines on the fly for large sizes.
@mzechner - have any code for that LRU glyph cache? It sounds very interesting.
Font rendering is indeed a pain in the ass once you escape left-to-right latin font languages. Even AppKit and the underlying renderers can be hacky in some parts.