Im pretty sure this is not possible without directly changing in the database, although is it possible to change the unique value per language option on Internal properties i.e. PageSortOrder ?
Not using PTB
I looked into this for you, but I couldn't find any easy way to do it. Had a plan of adapting the admin mode pagetype editor, but PageSortOrder is not in the PageType Definitions list, which complicates things. Let me know if you find a way, would be interesting to see it done.