Adding materia to Darklight/AF2 gear is on my short list of things to do as well..

Parry & Determination looks pretty good. Str/Vit if can get them without cap but doubtful that will happen much. Skill Speed, Dex, and resistances look like trash. Accuracy is a tough one to gauge - I'll probably skip it because doesn't seem like I miss much.

For Darklight jewelry, I believe it comes with Str or Vit, but not both. As a warrior, I'll probably add whichever one isn't already on my pieces.

Something I've been wondering though: Is there a warning when you're hitting a stat cap and requesting meld from other player? I know there is a warning when you're doing the meld yourself saying like "won't get full benefit".