I think perhaps a proficient example of this was with 'Desert Carnivores', which has since become a viewing area only for Yellow Mongoose. Which, nitpickingly, is not strictly inhabitat of desert..
I find it interesting to look at Marwell in contrast with a park similar in various regards, Cotswolds Wildlife Park. Granted, Cotswolds is indeed fairly larger [207 v. 140] but architectually, one could say they are somewhat similar, as zoos built around a manor etc. A contrast point, however, is that how in the last 10 years or so, the animal collection of Cotswolds has stayed relatively consistent in regards to animals - and the general esque of the park too is consistent, even in more recent exhibits like 'Little Africa'. Yet, Cotswolds seemingly practices a fine balance between consistency, and also that the park does not 'stagnate' - in that the arrival of new species is ocassional, but often greeted. [Tamandua, Hammerhead bat, Cassowary etc] Aside from some exhibits, the architecture of the park has not changed dramatically in the last 10 years.
Though that said, my optimistic side hopes that the contrast between the remaining 'historical' exhibits of Marwell and the more recent exhibits [e.g. Tropical House] as well as the relative short-lifespan of various exhibits of the late 2000s is simply signs of a transitional zoo - and that in the future, Marwell will be more consistent one way or another. I also hope that the future will see less such short-lived exhibits, which exist for a short while before blending in with the background..