Here's an in-progress Windows 64-bit build for you to try ahead of next release. I'm still polishing and solving bugs, and it would be most helpful if you could give it a try and let me know how you go.
https://developer.cloud.unity3d.com/sha ... Dsbow1O4nw
After you unzip, don't forget to add a font with Korean and Latin unicodes to StreamingAssets/Fonts. I've been using Google's
OpenSans for testing, which I've attached below for convenience. This DFU version does the dynamic glyph loading, so you should be able to skip the alphabet file now and it will load new glyphs at runtime. I'm curious how this works for you.
Just to set expectations - I'll do my level best to solve any problems within reason. What's not obvious here is just how much of the work is actually done by Unity engine and underlying operating system. I can't fix any bugs in Unity engine or with IME provider in OS, and the amount of access I have to the underlying IME system is basically zilch. So if something is outside of my power to fix, or proves very difficult to resolve for only a small improvement, I'll have to let it go for now. But hopefully what's shaping up here will prove to be "good enough" to resolve your CJK input concerns.