The current viewers are designed to meet the needs of all residents... and like any program that needs to do multiple roles it's processor heavy.
For film makers in second life it would be useful to have a viewer just for filming in SL.
In particular a viewer where the programming is about making the viewer as lean as possible... so that all the processing can be used to keep up frame rates.
It would also be useful to build an easy "change default camera position feature"... which would allow you to keep the camera on the avatar's face... and variable speeds on the camera controls... which would allow for slow pans and tracking shots.
The biggest frustration for me... and the largest barrier to the growth of film making in SL is the inability to control frame rates... the current trade-offs between graphical detail and frame rate just don't give you enough leeway to ensure you're always pulling 24 frames per second.
A dedicated viewer will encourage the growth of film making in SL... and there is huge potential in this. It could be the most important thing Linden Labs ever did.