Thanks for your bug report. This has been discussed before. Everything related to how strings are processed, displayed, etc. will need to be changed to a completely different set of APIs. It is a huge job that will require a lot of code rewriting, testing, and so on. This is on my to-do list.
That said, as you are looking into this, it would be helpful if you could research Windows string handling/classifying APIs and how they behave, eg. relating to upper/lower case, when it comes to characters in different Unicode ranges. I haven't looked into it recently but know from past research that these APIs often behave in ways that are not expected.