It’s not Thunderbolt - it’s just a USB disk enclosure with the cheapest possible 2.5" hard drive - yes, a spinning rust hard drive. The only thing you get over something $100 less is it stacks nicely with the Mini.
I’d say hard pass. What might work better is an external powered enclosure for the M.2’s, as that would reduce the power budget your Mini is trying to satisfy.
That’s essentially what I do. Bunch of drives, each formatted individually, then pooled with MergerFS. Get a new drive, add to the pool. If a drive fails, it only loses that much of my backup; rest of the disks are unaffected. All the advantages of storage pooling without the redundancy (which here is useful).
Best you’re probably going to be looking at is a Tesla card of some variant, and in a 1U without external power support it’s not going to be beefy. You’re not getting anywhere close to an RTX anything in that server.
As others have implied, you need to have something run on startup that will execute that IPMI tweak again.
In my case ESXi auto-starts my VMs, one of which is a docker VM and it auto starts a container that does the IPMI tweak (and monitors temps and adjusts and all that).
You don’t need to layer it this deep, but fundamentally you need things to auto-start on boot, including this.