One reason why I though FAT easy, is because Hatari emulator has scripts that create hard disk images from directory contents and floppy images from ZIP files, with Atari TOS compatible FAT file systems. I'm pretty sure Aranym can read those too.
But EXT2 is better for transferring unix files (long filenames, correct owner/access rights).
One more option would be to setup e.g. local NFS server and mount your host disk that way, or use local FTP/HTTP server from Aranym. Local Apache server is probably easiest if you've already setup networking from Aranym to/through your host.