There's no challenge getting a UK vat number after you pass the threshold. And without one you wouldn't charge vat so the client wouldn't need to deduct it. And a US llc can't easily get a EU vat id, so I don't understand why you don't use that argument against a US llc also.Uhm, no, thank you. I left the country years ago and the tax office never bothered me after. I don't want to give them any ideas, especially since I'm currently not a registered resident anywhere else.
Oh, I'm not against US LLCs at all! They sound almost too good to be true (provided you can get a bank account, which I've heard you can with Transferwise).
With UK Ltd.s, there's the challenge of getting a VAT ID, as long as they're still in the EU. Without a VAT ID, my clients would not be able to deduct the VAT.
The UAE still seems interesting as well. It would work for personal residency, I actually like the UAE and they seem to be implementing economic substance regulation. Maybe it's just a stupid fantasy, but I'm wondering how strictly the UAE actually implements those rules. Maybe it's actually a net positive?
If brexit happens you will not charge vat to a non uk client.
Apart from this, a lot of the discussion here refers to the actual laws and the facts on where you are or might be tax resident. If you don't want to ask your local tax office if you are tax resident there, then a lot of the advice here might not be precise. If the main goal is to not get caught then the options you have is different vs if you try to make a long term legal solution that will stand if anyone should question it.