We’re a bit like Tom in your example, and we’re currently working out how to become compliant. One aspect of this which I haven’t seen discussed yet is (quoting from your excellent article):

“his invoices comply with the VAT rules in each member state”

How on earth are we meant to know what each of the member states’ rules are for VAT invoices? The HMRC MOSS documentation seems to give no guidance on that, and as far as I can tell many states only publish their rules in that state’s language….