How difficult?

[Titan_Bow]

How difficult would it be to edit an existing airport with either a new hangar, or adding a logo/sign to an existing hangar;  and setting a "starting" point there so when you select that airport, you can select that specific starting spot?

[Scruffyduck]

You can use an airport design utility to edit airports and, in some cases, add objects.  Placing a sign on a hanger may be a bit more tricky.