How about compatibility and suitability for removable storage media? As far as I know, f2fs is just about only other suitable FS out there to compete as journaling file systems with somewhat complex acl's are not the best pick for such application.

AFAIC, Jolla would do best to offer some alternative (but suitable) file system from GUI, perhaps even LUKS (don't know if it could be done in a way that allows including needed software for Windows to work with it) but to completely dismiss exFAT because of licensing issues (as if there were no other licenses in Jolla devices....).