Nute can't be intimidated by Greivous, he's the one holding the leash. He should be instructing Grevious on all the horrible things he wants him to do to Amidala and the Jedi once they're captured. In Nute's mind, Greivous is working for HIM (even though he isn't). Unless we want to change it to where Greivous is the dominant role, and the Neimoidians are reporting to him.
It could even start with Nute saying something like, "And that, Lord Greivous, was the last time they appeared on any of our scopes..."
In any case, let's not draw attention to the fact that Greivous doesn't speak during the scene. In fact, he really doesn't need to say anything at all. All the audience needs to know is that he's in cahoots with the Trade Federation. It should just be played as if he's listening to Gunray intently and we just caught a snippet of their meeting.
No need to re-hash info we already know. We know they escaped. Now we know Greivous knows.
As for Rune, I think you've got him pegged correctly as the naysayer or voice of reason in the bunch. See, he's not cowardly, he just has common sense. But he's still greedy and he wants everything that can be gained by this plan if all goes well. His warnings are usually right, the problem is, no one listens to him because he's always getting slapped down by Nute and his wild delusions.
No need for the hologram to click on and off, the whole exchange is very brief, we're only hearing the most important part of their conversation.
Basically, it's:
Nute explains the situation to Greivous.
Tells him how he wants him to proceed.
Maximum of two or three sentences.
Greivous does his best "silent but violent" Sith Lord impression.
The name Sidious may or may not be dropped.
Rune interrupts with more common sense.
Nute slaps him down like a bitch.
End of scene.
So, as far as the actual dialogue is concerned, we need to ask ourselves, what is the point of the scene? The point is to simply and quickly establish the NAME of Greivous, the fact Greivous is affiliated with the Trade Federation and is now in pursuit of the heroes. Period. It serves no other purpose. This is not their first introduction to Greivous, we assume the Neimoidians are well aquainted with his work. He's not Boba Fett, he's not a hired hand. He's there as an enforcer for Sidious, to make sure everything goes according to plan, and that no one escapes. But, (I think) he should still be subordinate to Gunray. It's just like Tarkin and Vader.
I still believe his entire involvement in the story, as well as Anakin's role, would be strengthened if his sole purpose was to locate and retrieve the "vergence in the Force".
We have to be careful though. As we've seen with the Prequels, it's easy to fall into the trap of explaining too much. If you look at ANH, it just throws you into the middle of everything, and you kind of have to use your imagination to sort everything out. So, even if we make it ambiguous, I think the audience will still get it.
P.S. - Does anyone know where I can locate a German language version of Episode I?