My dream is that you could write to Google Drive or iCloud Drive transparently too if the browser allows you to

I believe you are able to connect to a Google Drive account with a purely client side site via google oauth and then using the Google Drive rest api. There was an article in particular that I liked that walked through it. Let me see if I can find it

	▲	Lord_Zero 8 hours ago \| parent [-]
		Yes but Google OAuth is a nightmare if you want to "publish" your client so that anyone can use it. If only you use it, you can add yourself as a test user. Just know your access token expires super fast and you will have to frequently re-auth. Its crazy annoying.