I'm the author of the article. After musing on the comments here I wrote a followup about improv HSMs. These aren't tamperproof and as such are suitable for us

I'm the author of the article. After musing on the comments here I wrote a followup about improv HSMs. These aren't tamperproof and as such are suitable for use in secure datacentres only. https://www.devever.net/~hl/improvhsm https://www.devever.net/~hl/improvhsm