How about making the Orbit (Right Mouse -Alt) orbit the landscape and not move the sky?
The Sky has two rotation sliders to move it.
The same would also apply to the Right Mouse to just move the landscape and not the sky.
Added after some use.
Is it possible to add multiple select for the move tool?
One of your visuals included a fence with several segments. If you wanted to move the fence it would be a trying task, but with multiple select it would be easier.