Using relative paths for assets for heroku deployment I cant quite wrap my head around the way the way the heroku file system works, so I'd like to use relative paths for my asset File System Paths. Is that even possible?

I've tried to use CRAFT_BASE_PATH in the general settings file to define an environmental variable, but no real luck getting my assets folders to be recognized.
Take a look at Multi-Environment Configs and specifically environmentVariables. Then you can add your variables to the settings in the Craft CP.

Note: you'll have to figure out Heroku's paths by trial and error or ask their support staff for help.