If they were going to do an Indy water ride, then using the Shanghai POTC tech would be the perfect fit (as opposed to something like a Splash style flume ride). High capacity, can allow for a decent amount of excitement while still being family friendly and would finally add a water ride to DHS. Combine that with a higher thrilled ride like a clone of IJA or even a coaster like the one in Paris and you have a nice small land. Depending on the setting (e.g. Amazon ride in South America, Nile ride in Egypt, etc) you could also have some good themed dining to correspond.
Regarding Star Tours, I see no reason to waste money to convert that to another theme. It's a great ride as is and money should be spent to expand the parks not change existing attractions (especially in DHS which needs much more total ride capacity). I'd rather see an Indy land placed in Animation Courtyard and then the Echo Lake area redeveloped into an OT Star Wars land keeping Star Tours as is. Just IMHO.