No suggestions from operetta yet? There are so many Savoy Opera tunes that could work here, from 'With Cat-Like Tread' for a march on down...Orfee aux enfers is an operetta and if P/C want to get all French on us I could see them doing something can-can influenced for fun (imagine Guillaume doing can-can splits!)...and there's The Merry Widow and so many more...
Plus there are some more obscure musicals. I'm a big fan of A Gentleman's Guide to Love and Murder which has some lovely rhythms, though unfortunately the best ballad ('Sibella') is a waltz and the glorious bedroom farce number 'I've Decided to Marry You' is a three-hander that wouldn't necessarily translate well to a two-person routine. 'You're a D'ysquith' has potenital though! And I'd love to see some West End pieces get a look-in: Matilda might not work for an adult team but a pair just out of juniors could have some fun with it. And what about Hadestown or Groundhog Day, or some of the other newer shows?
There will definitely be at least one Hamilton piece, I'm sure.
Finally, I can't remember if the junior teams have the same requirements, but if they do some of them might find good material in some of the more innovative mash-ups from Glee (yes, I know, but consider the potential of, eg, the 'Rumour Has It/Someone Like You' mashup, or a younger team with 'The Way You Look Tonight/You're Never Fully Dressed Without A Smile').
And yes, the Disney musicals - any one that's had a stage adaptation is available for use here, from Cinderella to Aladdin to Frozen (oh god, people, just let that one go). There's also a stage version of Anastasia to draw on.