So in a secure environment I can't write words in IPA? IPA requires mixing Greek beta and theta with Latin letters (but there's a Latin/IPA phi just for fun).
It also doesn't help ɡ vs g.
It sounds like any genuine solution is either not simple or excludes legitimate use cases.
Yes, the Unicode Technical standard identifies the Latin, Greek and Cyrillic (most of IPA characters) scripts as confusable, and recommends against mixing them in identifiers. Use in general text is fine though.
It also doesn't help ɡ vs g.
It sounds like any genuine solution is either not simple or excludes legitimate use cases.