Could "totally implausible" mean "impossible"?

Plausibility is concerned with appearance rather than truth. If something is implausible, whether totally so or not, then it doesn’t sound convincing, it doesn’t sound as if it’s possible. To say something is impossible, on the other hand, is to say that it really cannot be done, not just that it seems that it cannot be done.

I take Barrie's point that plausibility is primarily concerned with appearance rather than actuality. But I think there's a limit to how far one can take such strictly literal interpretations.

In most contexts, probable/possible mean likely/unlikely, but whereas the corresponding negated form improbable means not likely, impossible doesn't mean not unlikely - it means definitely not.

By the same token, convincing/plausible usually mean very believable/just about believable. I'm aware some people use plausible to mean convincing, but I think most people need something very/totally plausible to actually be convinced.

As John Lawler often reminds us, negatives [are] probably the most complex portion of English semantics and the weirdest part of its syntax.

And as Cerberus points out here, [probability] is a complicated issue [in the context of linguistics].

In my version of English, if something is implausible, it's unlikely, but at least feasible. But if it's totally implausible, it has no element of plausibility/feasibility whatsoever, and I personally do not distinguish that from impossible.