This is a feature suggestion for Apple.

I want the ability to turn off the Camera Roll on my iPhone. Not the extra albums that I’ve lovingly created and filled by hand, but the primary photo album. The one everything goes into by default. I want to turn it off and replace it with a better integrated Photo Stream. A Photo Stream that acts just like the basic Camera Roll until you turn Photo Stream on a Mac hooked to your iCloud account. iCloud is smart enough to see this already. When there is another computer that can sync, it starts to download photos from your iCloud account, leaving the last 30 days or 1000 pictures in iCloud. The next time you snap another picture, or the next time the date rolls over, the iOS device would trim down to the 30 days/1000 photo limit. The Mac would already have the images, so nothing would need to be done there.

Occasionally, your Mac wouldn’t be online for a long period of time. Perhaps you are on an extended vacation. Again, iCloud is smart enough to see this, and would have your iPhone retain more images than usual (to keep Photo Stream at it’s 1000 image limit). As soon as that computer came back online, and caught up downloading images, your iPhone would get the go-ahead to prune the images on your phone.

Simple, direct, Apple-like, and importantly, even less work or hassle for the end user.