Keith, I feel your dilemma and it sounds like you have been thinking about it a long time. That being said, you have been thinking about it a long time and still cant really affirmatively say, yes i need the F6. You probably want the F6.
Both are honorable reasons to lust for that camera, but the question really comes down to is whether you can afford it. If you need it, then the decision is easier. It sounds more like you really want it, then just check with your budget.
Personally, since I also own a D700, I'd probably throw a F100 in the mix, see how i Like it and then decide if I need the F6. Alternatively, i'd try and find someone locally who would let me try it out before purchasing. Lastly, if you have the time, you could ALWAYS resell it for the price you paid if you get a good deal (ie: 89,000 yen etc..)
You have a lot of equipment, just meditate deep on why you want to spend $1200+ on the F6 with everything you have. Every body you add just neglects another . Is that fair Keith to all your other cameras? 🙂