Question about safety of my backup solution

Hi all! Recently I decided to ditch Dropbox because the app simply stopped working reliably on my end (after being a customer for 12 years). It puzzles me how they could drive such a great product into the ground…

After reading a lot on self hosted clouds and many threads here on Reddit, I found that the best solution for me was to spin up Resilio sync. This is my current setup in the network:

• iMac Pro with selective sync in real time
• MacBook Pro with selective sync in real time
• QNAP NAS at home fully synced in real time
• QNAP NAS at work fully synced in real time

Only the NAS at work is always on. My backup solution looks like this:

• QNAP NAS at work syncs to externally mounted disk once a day (one way mirror)
• QNAP NAS at work syncs to Backblaze once a day (one way mirror)

Now, one loophole I discovered was that if I accidentally delete a file, it will disappear immediately from all the real time synced devices. And if I do not correct for the mistake before the mirroring to Backblaze or the external drive at work, the accidentally deleted file will be gone forever.

My question is how to solve that loophole. Unfortunately I need to do active mirror syncs for the backups because it would become simply too expensive to do versioning as I have lots of traffic in the synced files (100 GB per day, with many additions and deletions). One way I thought about was to trigger the Backblaze backup manually, so that I get a chance to at least review the current state of my file system before mirroring it. But any other suggestions would be highly appreciated.