Frage Fillet complex shapes

[ChrisFox]

I currently struggle on creating fillets between 2 complex shapes. For example the fillet between a wing and a fuselage. Bevels won't work because it stops on the first next edge it's meeting.

For understanding I constructed a simplified example in the picture below. 
   
The first solution in my mind would be to delete all the edges, that are in the way. 
   
But then you must know exactly how large the fillet will be in the end, which is not obvious all the time. So guessing is resulting in strange geo 
    .
For more complex shapes this isn't anywhere practical.

I hope I made it clear.
How would you tackle this problem?

[Malthea]

Hello,

LoopTools -> Bridge is your friend

At first you need a gap:

   

Select the border edges and activate Bridge

   

Subdivision depends on segments, strength creates the curvature