Using a non-FAT filesystem for portable storage opens up lots of issues regarding broken permissions. Try to create a file on an ext4-formatted USB flash drive using your current user; rest assured that, unless your remembered to set its permissions to 777, on another computer you'll have to chmod it because it still belongs to the possibly dangling creator's UID and GIDs. If you don't have root access, and unless coincidentally your user has the same UID as your other machine, you're screwed and you have to go back grumpingly to a system where you have administrative privileges.
Same thing applies to NTFS, but I've seen that more often than not Windows creates files on removable drives with extremely open permissions, and in my experience NTFS-3G just straight ignores NTFS ACLs on the drives it mounts, so more often than not it JustWorks™ in common use cases.
I think a journaled extFAT-like filesystem would be perfect for this task, but given how hard it was for exFAT to even start to displace FAT32, even if it actually existed I wouldn't expect it to succeed any time soon.
Same thing applies to NTFS, but I've seen that more often than not Windows creates files on removable drives with extremely open permissions, and in my experience NTFS-3G just straight ignores NTFS ACLs on the drives it mounts, so more often than not it JustWorks™ in common use cases.
I think a journaled extFAT-like filesystem would be perfect for this task, but given how hard it was for exFAT to even start to displace FAT32, even if it actually existed I wouldn't expect it to succeed any time soon.