It turns out that you can modify LEGO Star Wars: The Video Game. Examples:
Boga prototype
Dexter Jetster
Playing as a creature
Playing as a hail-fire droid
Playing as a jumbo homing droid
Playing as another creature
Mawhonic as seen in a cut scene.
Playing as Mawhonic
Playing as a pit-droid
Playing as a dwarf spider-droid
AATs replacing STAP guns and Separatist drop ships
AATs replacing STAP guns
Playing as WA-7
Wattos replacing genosians
Zam's speeder replacing Count Dooku's speeder bike