That sounds fun!
Yes, it should be possible to do. I have never tested TimeLapse for a full year but I have tested it extensively to ensure it should be able to shoot for a year. It has been used successfully in a 28 day time lapse session
You would use Classic mode and, as you said, would set the photos to be saved to the camera roll where they can then be iCloud replicated automatically, assuming you have a solid network connection. In addition, you want to take the usual precautions of ensuring there are no interruptions (e.g. no phone calls, shutting off reminders, etc.). you will not however be able to use airplane mode if you want iCloud to work.
I would urge performing a few day test run beforehand to shake out any issues and indeed to verify that photos are being accumulated as expected in iCloud.
I can't tell from your question if you have downloaded TimeLapse. If not, you can download the free version from the link below. It is limited to 59 photos but if you set it to take a photo once an hour that still gives you a two and a half day test run.TimeLapse - Free
I'm very interested in hearing more about this project as it progresses. Thanks!