Backup original video and then shrink

So I have run in to the issue of filling my iCloud (200 gb) with pictures and videos (videos taking up 80 percent of the space). So far I've figured to save all my original videos in a separate photo library on a harddrive, while replacing the ones in the cloud with shrunken versions, so I can still watch them on my phone and tablet. Most of the videos go from +200 mb to 10 mb. Saving alot of space. This I could of course do repeatedly every time my library gets full, but I would prefer if I cut automate it.

SO: do any of you have any great ideas or suggestions to tools I could use. I'm imagining it working a bit like this:

1. I record a video on my phone
2. The original video is automatically transferred to Dropbox (this I know how to do in IFTTT, but would prefer a Shortcuts solution)
3. The video is reduced in size (resolution) on the phone and replaces the original in the phones library and of course icloud photoes.
4. On my mac (running as a server) an automator script will then add the video downloaded through dropbox to a Photo Library on a hard drive with which is also backed up on my TimeCapsule. (This I think will be fairly simple to figure)
5. Video on dropbox will then be deleted.

I hope someone can help me with this. And if not then maybe spark some idea for a software developer for building a tool, which I would gladly pay good sums of money for.

If I find a solution I will make a guide for people interested here.

And to all the ones who would suggest using Google Photos, no thank you. I am not selling my data to Google.

TL;DR: Is there a way of automating resizing videos in the shortcuts app? Everything running automatically in the background when a new video is recorded.