Alright so I can use relative path BUT I have to put the absolute part of the path to the "texture search paths".
I need to use relative paths in case I ever want to move my .ass file and not loose the texture link.
If I used absolute path to textures and move them, I'll be rendering a lot of red. I am making a asset library and as I go I move stuff around so this is a no go.
So my only options are yet again workarounds. I made a custom script to remove the absolute path from .ass file and only leave the relative bit. And because searchpaths don't search subfolders and regular way of importing procedural in max is tidious, I also made a script to load the procedural and at the same time add its path to the search paths so my texture get recognized.
It works but it was a challenge to get there. Usd and fbx works just fine with relative paths.