So that means FOG would need to compile lftp for the FOG host server during install. I have not checked the lftp from FOS Linux but we would also need to ensure that lftp in FOS supports ssl too. We have a bit more control of FOS Linux support of ssl than the FOG Host server.
From my point of view FTPS (FTP with SSL) is no better than FTP from a firewall/network/security point of view and I wouldn’t spend a second on trying to make this work.
If we really think about making this part more secure I would want to push this down the SSH/SCP/rsyncOverSSH way instead! I have not looked into this yet but I could imagine we can make this work for 1.6.x some weeks down the road.