I agree with your sentiment that we should look to follow Barca's progression from keeper to keeper. I wouldn't be against him being our CL keeper, but first game of the tournament against possibly the second best team in Europe, could end up having more adverse affects than positive, depending on how the game goes, plus we would want to get the best possible result in our hardest game, so for this, I would be happy to stick with DDG then Henderson picks up the baton for the remaining 5.
Yes, it could be a risk, either keeper we play, but I wouldn't want to stick this pressure on the lad, he is still vastly inexperienced in this level (CL) and a mauling is the last thing he would want.
On the other hand, I can see why some would think a game like this 'could' be the making of him, but I don't think it is a risk we would be willing to try just yet, not with how we started the season. Just my 2 cents.