Hello,
thank you very much for your messages. After some tests I found out this limitation as well.
That only 16 bit WAV files are supported by GDScriptAudioImport in general is not so bad for my use case, but that all other WAV formats are not supported at all is.
For my game, for example, I would like to use the IMA ADPCM format, as this is also supported internally by Godot.
I will definitely keep an eye on your project as I see a lot of potential in it. The idea is really awesome and with a working WAV import it would enrich my general workflow immensely.
You guys are top notch and do great work! :)