I can't imagine any coding difficulty implementing a functional diplomatic system, as well as a trading system too... Time consuming? yes. Difficult? Nah...
Traditionally, strategy games always had abusable diplomacy system. Either AI was always getting a bad deals or it was offering deals to human player at such horrible rates that no sane person would accept them
I guess Illwinter decided to sidestep this problem by not even trying to implement such feature
As i strongly think more options are always a good thing, an option allowing or not in a SP game the diplomacy, alliance and trading possibility with the AI would be a fantastic addition to the game in my opinion.
It would even lead into another victory condition, allied victory (in the case of the game storyline, maybe that could translate into the birth of a pantheon instead of a single pretendant accessing godhood)
I've always loved diplomacy and trading in Strategy games and think this would be an awsome additon to an already wonderful game. How about it Illwinter???