Kach and Corise are going to work together? I find that prospect amusing and a little... unbelievable.
Can you have provisional force ranks? As answered above - no. You can put in the leg work and earn your way up. Keep in mind, however; as you're building a Force Faction that until such time as your lead characters do have a noted OOCly Force Rank you should avoid any extra-planetary entanglements as these would be short lived and likely result in three very angry members and one or two very amused Sith characters/members.
Are you going to fleet? If so, I'm gonna stomp my foot and say no. You three, fleeting together, is a very bad idea. I don't think I have to explain my logic behind that statment. Do like the Force Ranks, near as I'm concerned, and spend some time in the kiddy pool before you go mucking about in the Galaxy proper, kay?
Another new group... and not a bad idea, but I have to ask myself "Why do these people need a whole new faction for what should/could be reasonably explained as a subfaction of TSO or what-have-you?" Can you honestly answer me that without resulting to "we don't wanna be a subfaction" tripe?
I do not think that the Dathomir Witches need to be a faction of their own, and if they do, I do not feel that the faction needs to start as an independant entity. Given the recent abuse of Faction Creation I'm naturally somewhat trepiditious about this given that two of the membes involved already run their own factions/subfactions. I feel like many of our members have been abusing the growth process and just leaping ahead with their super-uber factions, which is BS.
I know that the three members involved have more potential to make this thing a sucess then should be required to see it fly, but also taking into account your histories, recent faction abuses, and the general misconception about faction creation that I am a little nervous about the prospect.
I do not know that you can assuage my concerns either.