I do agree that the Souleater finisher doesn't really fit as a combo finisher, but based on the DRK in the background of the Sage reveal for 6.0, it looks like Souleater combo's here to stay sadly.

In regard to giving it something akin to GNB's weaving combo stuff, I feel that would just bring out a similar issue like how people don't like Delirium being a discount Inner Release. It would just become a "Edgy GNB" instead of discount WAR and wouldn't help DRK's identity issues. There's very little they can switch around at this point that wouldn't just be a form of homogenization, be it for better or worse (i.e. giving it a DoT like Scourge and an alternate combo finisher).

As for reworking Delirium itself, maybe one thing the devs could do is incorporate an attack speed aspect like Blood Weapon used to have, among other possible effects. But at this point who knows what they'll do. Based off the Endwalker trailer with PLD blocking with a very telegraphed and glowing and then smacking the one enemy, I wonder if tanks will get a sort of SAM Third Eye-esque "get hit and then counter" system. That might open up cool ways for each tank including DRK to have their own means of retaliation that effects and interacts their gameplay and other skills.