A UI Overhaul would be great.
It's pretty nice now but I think it could be better.
Also adding buttons to create like a Protoplanetary Disk and Etc.
I agree. Although instead of completely replacing the UI in a single update it will come in over several updates.
The next update will probably have a new on screen HUD that will allow you to change gravity, time step, and enter chart mode without having to click the right mouse button.
I also plan on updating the introductory tutorial in the next update.