If you buy the d7000, are you still going to want the d700?
Can't speak for the OP, but do I want the D700? Probably, although I'm more interested in its successor considering how close it's supposed to be. Am I happy with the D7000 anyway for now? Most definitely. Would I ever sell my D7000 upon upgrading? No, just like I didn't sell my D60 when I bought the D7000 - always good to keep a back-up. So if I now bought the D700, I'd be in the same boat - I'd be happy with what I had, but of course I'd want a D3s (or its successor). And honestly, if I had all the money in the world I'd go for a Hasselblad. But I don't have all the money in the world and I'm super capable of being happy with what I have when I have it. The D7000 is no replacement for the D700, but it's a very good, lower priced alternative.
Another thing to consider is that nobody goes from zero to pro just by purchasing a better camera. An enthusiast level cam like the D7000 may be a smoother move from the entry level D70 than going for the pro level D700 straight away.
If you buy the d7000, are you still going to want the d700?Will there be that thought in the back of your mind that for a little bit more you could have gone fx, and made the most of that 24-70?
That 'little bit more' is like 1000 quid. Quite a difference, methinks. The longer you have to save to get what you (think you) really want, the longer you're shooting with something you've obviously long outgrown. There is no harm in adding an intermediate step to the upgrade if it means you're going to get more than what you currently have.
IMHO No point paying twice, and not getting what you want.
'Want' isn't static. There'll always be things one wants but can't have yet - particularly in the heavenly realms of photography equipment. Doesn't mean one needs it though, doesn't mean one can't be content with what's there. Coming from a D70, shifting straight to the D700 is a huge jump. Going for the D7000 and splurging on some fab glass first is already going to make a huge enough difference that the OP wouldn't be sitting there with regrets.
The 24-70 will act like it only goes as wide as 36mm at the wide on a D7000 end so quite limiting if you want to shoot wide.
I'm sure the average person buys a lens for the IQ it delivers more than the exact focal length. I still don't own an FX camera but I would never consider buying a DX-only lens. The 24-70 is a legendary piece of glass, no matter what you mount it to.