Considering the same patch applies to Cubase AI 7 and 6, have you guys simply tried installing the patch over 6.5.5 on OSX 10.9?
The patch is available here: https://www.steinberg.net/en/support/knowledgebase_new/show_details/kb_show/steinberg-product-compatibility-info-regarding-mac-os-x-109-mavericks
I do my music production on Windows 8.1, but do have an iMac in the other room which is still on Mountain Lion so I can’t really test myself at this stage.
Good luck! 