Solas’ line to the Inquisitor about not giving them the tools to stop him has always stuck with me.
I believe we met Abelas and the ancient elvhen for a reason. I also think the Well of Sorrows mattered, whether the Inquisitor or Morrigan drank from it. The sarcophagi in Trespasser, especially when paired with Cole’s comments about voices crying in the dark, always made me wonder if those coffins held ancient elves, newly crossed spirits, or some combination of both, trapped in stasis. Either way, these are Solas' people that he's trying to save.
That makes me wonder if the “tools” Solas refused to give the Inquisitor were the ancient elves themselves. What if, once the Inquisitor understood what was really at stake, they committed themselves to finding these slumbering elves and awakening them before Solas could? What if they tried to reach his people first, not just to use them against him (though that could have been a choice the Inquisitor made), but to understand him more and find another path?
Through Abelas, we know at least some of the ancient elves can be reasoned with, work together towards a common goal.
And imagine if Solas had revealed, even then, that he had once been a spirit. A high-approval, romanced Inquisitor, might have been uniquely able to appeal to his original nature as Wisdom. The Inquisitor already reflects him in so many ways and I can see this being a very big reason why a romanced Solas refuses Lavellan joining him. Lavellan would find out more about him, he'd naturally want to share more about himself and in doing so, make him more vulnerable to Lavellan's understanding and connection.
Had the Inquisitor known the truth about Solas, about spirits manifesting, about the ancient elves, and about what he was really trying to do, that knowledge could have become the very thing that helped them reach him.
DAI spends so much time showing us that the Inquisitor is shattering glass ceilings all over the place. They enter the Fade physically, they enter the Crossroads and walk through ancient elven spaces, uncover forgotten history, and repeatedly pass through places tied to spirits, memory, and old magic. These are exactly the kinds of places where the Inquisitor might have searched for the ancient elvhen if they had understood what they were looking for.
So I keep thinking about an alternate path where the Inquisitor gets there first. They find the slumbering elves. They awaken them. They pass through trials, earn their aid, and learn enough to confront Solas.