What might be the recommendation file system for a grub partition, so that it will be accessed from most of linux or windows or osx systems.
I'd stick to the defaults, an ext* filesystem. Personally I use ext2 because the journaling function of ext3/ext4 can make mounting the filesystem slower (observed on a flash memory stick). AFAIK journaling can be disabled for ext4, but since I was happy with ext2 I did not consider ext4 for read-only partitions like
Avoid filesystems that do not support Linux file permissions like NTFS and FAT*. Although all files are owned by root and most of them have permissions 644, lack of proper permissions support could set inappropriate default permissions for the files.