Sounds like an awesome plan! Although, since Ashla's relationship with Tobias wasn't exactly spiteful, she probably would have sent him after someone else. Making that someone a useless NPC should take no time though xD

At t this point Ashla knows how deep she is, but has no idea what to do or where to get started. She is currently in Scara Brae, one of the few places she isn't wanted for anything. Maybe since they're both wrecked with guilt and self-blame, Dirks makes a suggestion and they go with that? A sibling-like relationship sounds awesome for them!

Another point to add, I do think that the reason Ashla would spare Dirks in their first meeting was because she saw that he and Kyla had some sort of positive relationship, as he did protect her. That probably came back to her and she just sent him on a far off, likely to take a while mission instead?