custom roms – Android Nougat on Emulator, editing /framework odex files

Since three days right now im trying to modify odex files in an emulator without any success (LD Player, i only have one phone).

I also found 10 years old guides on XDA and outdated tools, my question is now is it even possible to edit/modify for example /system/framework/oat/x86/(am.odex, content.odex, services.odex or settings.odex) files without creating a own AOSP (Android Open Source Project).

What could i do already:
I could dissambled odex files (for example. framework/oat/x86/settings.odex) with (smali.jar/baksmali.jar_2.4.0) and modified the code and compiled it back.
Then i used “dex2oat” to create a new odex-file, replaced it on the emulator, started it and failed.

I hope someone could tell what im doing wrong.