But surely taking legal advice does that? A qualified professional tells you what to do, you do it - what more is reasonable to ask?
I am pretty sure there are some situations where you are still personally liable, regardless of what advice you took. Even if it was paid for legal advice.
We've already established that lawyers aren't liable for incorrect advice.
If HMRC do accept that advice can be incorrect and generally allow the taxpayer to correct the account without further action, then I don't see why AR should not be treated as any of us would. It's sub optimal, but at least no special treatment.
It would be the special treatment that makes it a resigning offence.