Make it a variation of KSP
I think these should be added to SR2.0.
Melvin and Kelvin the Astronauts (the dummies from Dummy Defense) They would have health bars in the mission, and they could die if ever something bad happens.
Large Landing Legs, cause why not? SpaceX mate!
Reentry. Would love to see a spectacular firework display as well.
Multiple Command Pods. This would be very useful for reusable rockets.
Gimbal Locks. So RCS isnt too costly. However, it will be powered by batteries.
Basically everything from SR1 and SP. Would like to build a Pegasus launch vehicle someday.