I disagree. The definition of plausible is "seeming reasonable or probable".
To say "the idea is completely possible" might be accurate but has a completely different meaning.
A security researcher discovering malware that infects several different BIOS types including on PC and Mac hardware with every major operating system that can spread via USB and communicate via sound between standard speakers and a standard microphone over distance and then going about his normal day-to-day life over the next three years is the very definition of improbable.
That's Google's definition, which in my opinion doesn't capture the word correctly. That definition implies "plausible" suggests "likely". Turning to Webster:
1 superficially fair, reasonable, or valuable but often specious <a plausible pretext>
2 superficially pleasing or persuasive <a swindler… , then a quack, then a smooth, plausible gentleman — R. W. Emerson>
3 appearing worthy of belief
To me, an idea is plausible if I can entertain the possibility without suspension of disbelief.