I think with your alternative point, it's that such a test doesn't really exist, not to the extent that it'd be comparable to being double vaccinated in the "safety" stakes.
A LFT is quick but has a very small window of being useful, and a PCR "to make sure" is accurate but takes days to get results, so you're sat waiting for results when you could have been infected in the meantime unless you've isolated, and such a "to make sure" test is not encouraged unless you have symptoms I don't think, because of load on the labs.
Vaccines reduce transmission significantly, so if you're in a double vaxxed crowd it's actually safer, even if someone still has it, for you and anyone they give it to.
If there's people who just have tests, if the test missed it, they're more likely to transmit it than someone with a vaccine, and if they get it it'll be far worse.
I do totally understand the ID concerns (although I think the time to be concerned for our privacy and have it actually do something has been and gone) but wouldn't be adverse personally to them if they are short term, like they last 12 months and then we see where we are, if the pandemic is still ongoing to the same level (I know covid will be with us for a long time) and they're still necessary then reissue or reactivate them, however it works, but they should be strictly for medical purposes and have no other tacked on shit in the future, I'd appreciate that being made into law if they come.
I'm not going to say I know everything about the ID debate though, so that might be simplistic or daft view on it.