Im sorry if this has been done, but adding new campaigns and illnesses and animations would be a pretty cool feature. Almost like an add on pack.
Also adding new objects and Staff, such as latino, middle eastern etc. All we seem to have with TH is Black and White.
There could also be male nurses and female doctors, sisters and one off prescription drugs to boost revenue from a dedicated pharmacy for certain infections.
It would also be nice to be able to build an already running level that has been run into the ground and you have to build it up.
Just a couple of thoughts. Its a shame Bullfrog never did EPs.