This has actually been talked about quite a few times on here, and the thought is that it would be virtually impossible, for a handful of reasons.
The "lake" at AK in front of Everest doesn't have a concrete bottom.
The "lake" is connected to the river that runs around the tree of life. That would all have to be changed.
The waterways at AK have plenty of fish/turtles/wildlife in them (it's kinda part of the theme of the park, no?). That would be a bad mix with a highly technical fountain show.
There's no infrastructure in place for something like that in that lake.
That's just a few of the reasons. There's also no viewing area for something like that. That's not to say that any of these hurdles couldn't be overcome... But that takes $$... And we all know how TDO is about that. Why would they do all that, and spend all that money, when they've got a perfectly good lagoon with tons of stadium seating already built that would work great? Or if they didn't want to go that direction, I'd still imagine they could build another facility from scratch for the same or less than what it would cost to make it happen in the lake at the AK.
The simplist solution is usually the correct one... A show themed around Disney movies makes sense in a park centered around movies, in a theatre and stadium already there and ready to be converted. Zero chance it would happen anywhere else on property, IMHO.
Welcome to the boards, by the way!