Having no luck with various programs i decided to try "Tile Molester Mod" again:
https://www.romhacking.net/utilities/991/
And after some initial trial and error i finally managed to get our beautiful and ugly GL6 font to display!:
And here with another codec, 4bpp linear, reverse order:
I sadly didn't find any clue on getting a variable width font to work on GL6 yet.
I am pretty certain that the guys who did the official GL5 translation did the following:
1. created a better font
2. created a vwf code to let it display properly
Now, i believe that the developers of GL6 didn't care about the font code and didn't include it in GL6...
So, i imagine that i gotta somehow create a new function that has the GL5 VWF code in GL6 and after that let the "text display" function point to that code.
No idea how to do any of that, but i will keep on trying.
If someone has knowledge of programming, VWFs and stuff like that, please write me a mail!
For anybody interested, heres how the GL5 font looks like in the tile viewer: