Except we're not; we're trying to get adequate guarantees...

Sure, that's a more accurate phrasing. Though I don't understand how "adequate guarantees" can be harder than "strongest guarantees possible." Anyway, you can substitute "adequate guarantees" into my sentence and it still makes the same point I wanted to make with that sentence, and still makes the analogy to contemporary high assurance systems.

The main image reason I object to "safe AI" is the image it implies of...

That's roughly why I prefer "AGI safety" to "safe AGI." What do you think of "AGI safety" compared to "Safe AGI"?

Which brings us to the other image problem: you're using a technophobic codeword...

I raised this in the OP and my response was "I've not actually witnessed this in reality, and contemporary AI safety researchers seem to be doing fine when they use the word 'safety'."

"Friendly AI" is there to just not sound like anything, more or less, and if we want to replace it with a more technical-sounding term, it should perhaps also not sound like anything.

I think these days it sounds like a companion robot, which didn't really exist when the term was invented. But even then it might have sounded like C-3PO. I do like the not-sound-like-anything approach, though. Possibly via Greek or Latin roots, as you say. Certus-AI ("dependable" in Latin), or something like that.