if your a lawyer its obvious you dont do copyright law (i have had 2 occasion to deal with them, so do know a couple things)
“Say someone uses your runway texture mod to enhance an airport, you can not enforce original copyright to it”
that is Totaly Bogus and Incorrect, almost ALL copyright includes clause for derivative works, most copyrights do not Allow it at all, and you would Certainly be in violation of Any original copyrights if they did not allow this and you use someone elses intellectual property - this is Exactly the point of a copyright mate
here are the 2 i use most, 1 allows derivative work 1 does not
Creative Commons Attribution-NonCommercial [CC_BY-NC] license
https://creativecommons.org/licenses/by-nc/4.0/
Creative Commons Attribution-NonCommercial-NoDerivs [CC_BY-NC-ND] license
https://creativecommons.org/licenses/by-nc-nd/4.0/
Any use (no Matter some Company Policy) of materials from the second one is a violation of that copyright and probably illegal (region dependant)
Nothing in a Company Policy will change that