I think the giraffes will suffice for crowd-pullers rather than bringing in white tigers, animals with absolutely no conservation value, never mind the fact that they already have a pair of tigers in the park.
Honestly if I were to ‘replace’ the pandas with anything ‘crowd-pulling’, I think with just a couple adjustments, their existing habitat wouldn’t be adverse to a couple of gorillas (Though it might suffer in comparison to Budongo)
Why not use their enclosure for another bear? It’s not like they already have a species of bear that is just as threatened, a similar size and in dire need of an enclosure upgrade