I'm about to leave the Curst Prison and was wondering if I should replace anyone with Vhailor or just get him to attack me since I apparently won't be coming back.

According to Shrines.RPGClassics, "if you already have a full party and don't want him along, there are a couple of ways of convincing him to kill himself instead (90000 exp)."
I've only found ways to anger him, however, so I assume that this has been altered by a patch or mod.

I have Morte, Dak'kon, Annah, Ignus, and Fall-From-Grace with me while Nordom's holding the fort back home (Sigil).

I'm mainly interested in the dialogue that commences when certain party party members are present (Grace's comments with Trias and Vhailor, her [spoiler]romantic[/spoiler] comforting in the Civic Festhall's sensoriums, and Annah's confession.

I've noticed that, excluding the conversation with Ravel, Ignus hasn't said anything since I've gotten him. Does he have any importance or interaction beyond combat. Hint it. Don't spoil it.

Ignus has some conversations with the Nameless One, just like any other NPC, if you talk to him. He never talks with the other party members, and is definitely the character to ditch if dialogue and comments are what interest you.

Thanks for the help. I left Vhailor behind.
As soon as I finish this, I'll play through Lara Croft and the Guardian of Light.