This is definitely a good brute force strategy I ... think there’s another technique that relies a bit on trusting the printing drivers to do the right thing, where you can tell Ghostscript to print your document, and target another PDF. This should at least remove interactive components in a PDF
It's definitely brute force, in that it's the equivalent of printing a document onto paper and then scanning it back in. This "flattening" is highly effective at sanitising, but also removes all the semantic content in the process; the output should be several times larger than the input (and if it isn't, then it's an indication that something very suspicious was in the input....)
Indeed, I was hoping for something smarter, that would remove only the "risky" bits of PDF, but keep the overall structure (and size).