Question

Which word if substituted for gordian would best retain the meaning of the phrase

Answer 1

"Gordian" is an adjective pertaining to the ancient king of Phrygia, Gordius. This king tied a knot that can only be undone by the person who was the right fit to rule Asia.

As you can see, this adjective refers to something rather difficult and sophisticated.
Therefore, synonyms for this adjective would be: sophisticated, complicated, obscure or convoluted.