A helpless opponent is one that has for all intents and purposes a Dex of 0. Surprised opponents are denied their dex bonus.
Technically it makes sense. Surprise round only. I would say it wouldnt work just on normal SA but out of nowhere and the guy is taking a dump or reading a book isnt much different from snoozing.
Thoughts?
You've wandered into the Adventure Card Game forum. (And hey! Keep it clean!) (j/k)
Flagged. An dual-class forum member (PACG/RPG) may be along in the meantime to answer your question.
Dex of 0 and denied Dex bonus to AC are two very different things. Coup de grace only works on helpless opponents, and being flat-footed does not make you helpless.
If you want to houserule otherwise then go for it, but keep in mind that coup de grace is a full round action by default and you only get a single standard or move during a surprise round.