Tales and Chronicles
Jewel of the North, formerly know as vincegetorix
Differentiating weapons more, especially by having monsters be more or less vulnerable to different kinds of weapon damage, would change so much about combat for the better! It would give a reason for characters to be proficient in more than one, and therefore make it matter that fighters have so many. It would force more tactical play, and it would give a reason to keep a magic weapon that wasn't your favorite.
Sadly I think the survey showed that more tactical module would be less well received. Unless you count this a being ''more differentiation for weapons'' in which case I think that the community would love such system.
No need to be fiddly. Have different material useful against a specific enemy type. Have light rules for increasing the + of your weapon. You could even give an edge to the fighter to enhance their weapons themselves on downtime.
And for the love of god, avoid having a magic weapon ignore 90% of the game resistances/immunities! Magic should only be a trait as powerful as Cold-iron or Silvered.