One big thing that's changed since this thread was created is the ARM transition is officially happening. Maybe the best option now is to just invest in an ARM-based Mini. It's a lot simpler than installing a new hard drive or SSD, especially if you weren't planning on doing the work yourself. ARM-based Macs are the future, and will be supported much longer than Intel-based ones will. And finally, ARM-based Macs will almost certainly be cheaper than their Intel versions. We don't know pricing yet, but a new ARM Mini might not end up being that much more expensive then the parts (and effort) to rehab the 2011.
The 2011 mini is a fantastic design and it's really easy to change the HDD and RAM, so I don't see why you think it's simpler to spend $800 or so than $100 and 30 minutes.
Also, the 2011 with it's Sandy Bridge CPU will run windows 10 beautifully, that 2011 mini is an excellent windows computer.
I disagree that ARM-based macs are the future. They certainly aren't for me, losing windows support is a complete deal breaker for me. But time will tell what happens with the mac lineup 5 years from now. I have a 2017 MBP, I'm just trying to decide between a last model intel MBP when it shows up in the refurb store or pick up an Asus Zephyrus this year which will be my first non-mac laptop in nearly 25 years of mac ownership.