We do plan on adding FTP (and it's variants), However, we are waiting until after we have a stable release to add any more providers.
You can see the "master list" of requested providers and their status here:
http://community.covecube.com/index.php?/topic/1225-why-isnt-xyz-provider-available/
From what I have tried, StableBit is by far the most ... Well, Stable, network drive emulation program. I tried looking around to make sure before posting, and it doesn't look like anyone has asked for this yet, and since you guys allow for local drives I assume you are not exclusively service minded.
I think many people would love to have FTP/SFTP support in StableBit to allow them to use StableBit for "personal cloud servers" as-well.
Emulating FTP with other programs like NetDrive is not matured feature wise, and thus unusable for serious use.
