I think this will be pretty cool, if executed well. I've never experienced Haunted Mansion Holiday at DLR, but I can understand at least some of why it isn't at WDW - different demographics. At DLR, the crowd is mainly locals, APs, day guests, etc. At WDW, there are people who save their whole lives for ONE trip, and they have heard about all of these amazing things (yeah, I know I am repeating keys to the Kingdom script stuff, but you can't argue that it isn't truth) that are classics. If they are going to play with the classics, they must be played with respectfully. From videos I have seen, HMH at Disneyland completely alters the Mansion experience, in a way that would be cool to people like myself, who go at least 5-6 times a year. It'd be different, fresh. But to a once in a lifetime guest, who may never be back, that *may* be dissapointing to see the classic Haunted Mansion, one of the greatest Disney attractions of all time, overrun by modern film characters (albeit ones from one of the greatest hybrid holiday films of all time).
Jungle Cruise as Jingle Cruise however, wouldn't be that way. The Jungle Cruise is special because it is different each time in some way, and because of its storyline, setting, and atmosphere, I feel that doing a holiday overlay would actually add to the experience at WDW.