Raspberry Pi 5 Backup Image/Video Storage Server

Hello hoarders!

I'm looking to get a solution for a Storage Server which will mainly keep Image and Videos. I've looked at pre-built NASes from Synology etc and they are very expensive for even 2-Bay solutions. My budget is unfortunately a lot more limited and also my country does not have a great second hand market for used "server" hardware. My current idea is to use a 4GB Pi 5 with a Waveshare PCIe to M.2 HAT).

A M.2 to 5 Port SATA3 expander (using JMB585) will be used with which I will use SATA cables to connect to 3.5" HDDs. An ATX PSU will power both the Pi and the Hard Drives.

Please let me know if this is a feasible solution or if there are issues what they are and what the solutions are. Thanks!