Most video cameras shoot video and give you what you get/set in camera. It's like shooting JPEG on your DSLR. There are very few motion cameras that shoot RAW. The RED ONE, Dalsa, Silicon Imaging, Phantom etc, which are all movie cameras or specialist cameras. I know the RED, being the camera that I've worked on, where the choices you make in camera are metadata and are changable afterwards - white balance, curves etc. just like on your DSLR.
However, even with normal video, you can change the look of clips, to an extent. I'd use FCP rather than iMovie, and after import set up your project. You can apply filters to the clip itself, rather than to that instance of the clip on the timeline, so that next time you use that shot, it comes with it's filters set up the way you want. That might do it for you.
I'm currently 'missing' 2 workflow actions when importing clips:
1) are there any options to easy add meta-data to clips? (Just as with exif/xmp data on photos.)
2) is there an easy way to do perform a preset set of actions (sharpening, color correction, ...) during 'import'
Actually, I'm kind of missing a kind of workflow tool for videography like Aperture/Lightroom for photography. This has become an issue since I tend to shoot a lot more clips then before, and have a rather large archive 'readily availble' on readily available large harddisk. I think I'm not alone on this, since video is becomming more and more accessible.
I love the way iMovie works actually, cropping, easy layout color correction, etc, but it's not a complete workflow tool yet.
Looking forward to a LightRoom for clips. :-)