You can always use the set-fov command to override any changes the player may have made to that.
The main thing you want to avoid using are subtitles. Last I checked, neither the text nor its position scaled properly with the resolution, and they become nearly unreadable at higher resolutions. Training messages are a better alternative, although I can't remember whether hud-disable-except-messages keeps that visible or not.
In some rare situations, things may also look different depending on whether the player is using an original Volition model or a media VP model. The only way to get around this is to have two different versions of the cutscene mission, since the game has no way to internally identify which model it's using.
