I also vote YES on removing the celebration scene. I believe the scene had its merits, but it's all or nothing, right? I'd lose it for the sake of a more somber ending. That's how I always wanted it.

I LOVE the idea of continuing the funeral theme into the credits. The STAR WARS theme, just like the Gungan celebration, disrupts the the mood. My suggestion: Use the "Birth of Vader" theme from ROTS, which is basically an extended encore version of Qui-Gon's. I've always thought the QG funeral theme was somewhat out of place in ROTS.

The Neimoidians, that's a tough one. I prefer MagFan's approach of radically modifying the Trade Federation sub-plot, but the reversed Spanish was too obvious to my ears. In general, reversed speech always sounds more unnatural than alien. What I would do is to borrow speech from KOTOR or some other games with random alien speech.