big Thunder is actually a terrible ride....but not worth getting rid of...
3 lift hills? thats almost coaster designing sacrilege...especially for a height of about 60 feet.
but anyway...disney does not take down rides on a whim...often they don't take down rides long after they should.
all disney rides - particularly at WDW - are built for capacity -to "eat up" 3000 riders per hour. Thats the point. to keep large crowds occupied.
No way they ever take big thunder down anytime soon...and they aren't even willing to take rides offline for much need refresher timeframes - because of the loss of capacity.
take space mountain last year: they did a cool upgrade at
disneyland (the second space mountain - not the "iconic original") in 1999. It's a great twist on an old ride concept.
Couldn't bother to put either the dollars (a pittance by WDW standards) or the time in for the refit last year. all they did was shut it down for the bare minimum so that the thing would stay on the tracks. just because it eats guests (figuratively...not literally...the yeti does that...wait a minute).
So it is with big thunder. this thread is an interesting question...but in reality its not even in the realm of possibility from up here in the cheap seats.