Yes you can — iCloud can be used to sync anything that you wish.
- Open ~/Library/Mobile Documents and create a folder (call it anything you wish).
- Inside, put whatever documents you would like to sync over iCloud.
- That folder will sync with other Macs (and jailbroken iOS devices, and on the web too if you have a Apple Developer licence).
Alternatively, you can symlink a folder on your Mac in to the Mobile Documents folder so that the files remain in their original location.
Time Machine is a Backup Tool, not a File-Management Agent.
All it does, is copying new files to the HDD (as a mirror) and all older/deleted files go into a time-stamped archive.
If the disk is full, time machine deletes old stuff.
I assume you want to manage the data. Nit really "backup".
Because you do not copy them, you move them to the disk.
I also assume you have 2 Hard-Drives (1 for you and 1 for your wife), that should be in sync.
So in total you have 2 Macs and 2 Hard Drives.
Now Unix has a very popular command called 'rsync'.
You can sync (copy) or move data via rsync to the Hard Drive.
Rsync is command-line based, so it is a bit difficult.
But i would recommend it for your situation.
And because I was bored, here is a starting point for you.
Best Answer
You can use iCloud either to backup your iDevices' data and also as storage for your personal files, just like those saved in your HDDs disk.
Where?
As you said, instead of saving those files in your iCloud folder in your Mac, you can go to the
iCloud website and login with your own Apple ID credentials.
How?
After you've logged in to your iCloud space, you'll get to the main screen where you can see all the Apps you can launch directly on the website (Photos, Numbers, Keynote, etc..). You'll want to launch the iCloud Drive app, and once in it you should see 5 buttons on the top of the page.
The button you're looking for is the second starting from the left: the Upload button. It will pop up a window where you can browse your entire File System with, and search for the files you want to upload to your very personal iCloud Drive. After you chose the files, it will start automatically to upload them up in the cloud. Once done, feel free to delete those files from your Mac/Computer and access them whenever you wish, directly from your iCloud Drive App, which can be found either on the website we've just talked about, or even inside your iDevice.
If you haven't activated it yet on your iDevice, simply do the following:
SettingsiCloudtabiCloud Driveoption and switch it toON.You now have the App visible and accessible directly from the Home screen of your iDevice!
Note!
You're free to use iCloud as a storage solution, but I feel like you should remember by default you get 5GB for free on iCloud, if you want to upgrade your storage capacity, you'll have to pick a storage plan. At the moment there are 3 optional plans for iCloud storage:
The price will vary depending your location, you can check this article from the Apple Support website to find your own location's prices.