From my standpoint, ext4 and xfs are the primary supported root
filesystems. I don't think that anything else should be release
If this is the case, we can explicitly list the supported file systems in criteria. The list would need to be extended with at least vfat, which is used for ESP, though.
If we go this route, it would be nice to communicate this somehow to the end user, directly in anaconda interface. Either by showing a warning when a "not officially supported" filesystem is selected, or by hiding those filesystems in dialogs when creating a new partition (with a documented override).