That is true, it is basically impossible to animate a loading screen.. Also, why would you wanna waste the time to make an animated loading screen? People aren't going to stare at it for more that 5 seconds

Anyway, if you can pull off the HUD that would be amazing. I doubt you could though. The perspective in Halo 3 is basically part of a new game engine.. sort of. Halo 3 HUD perspective actually sort of looks like the MC's helmet, I don't think thats possible in Halo 1.