You should talk to Alee and Arsonide on how feasible your plan is since they are working on games of a similar nature.
it is - will not be, much more complicated then Elite, or Wing Commander Privater
I played Privateer (awesome game BTW), but what you are describing is a lot more complicated than privateer with walking around the ship and walking around planets. Now if the ship/planets are meaningless random settings then it is probably not too bad, but when you start to add realism then it is going to be very complicated.
I'm not saying you shouldn't try to make this game (it is my dream game btw!), but look at the number of people involved in making Privateer and how long it took to make. Granted, development time is faster in Construct and you don't have a team to coordinate with.
My suggestion is to experiment with making tiny parts of the game. If it seems feasible then go ahead and make the game. You will learn in the process and maybe pick up a few techniques to make your game more sound.