The Mummy can stay...it just needs a heavy effects upgrade, that's all. It neesa projection effects similar to Space Mountain Ghost Galaxy added inside the coaster segment, and an all new ending.
Also, I'd personally slow the ride down JUUUST a bit (if that is possible) to increase the ride length time. It's way too short.
What's sad is that the ride building IS huge. It might seem small in composition to the Orlando version and because the ride length time is short, but it really IS a massive building. ET was a pretty damn big dark ride! Stick the Mummy into the Indiana Jones Show building and it will also be short. The park really frikin needs a ride like that.