In the situation what is at stake is:
* Do I get to oblige a new fiction that I can pursue in order to solve my problem?
or
* Does my effort complicate my life.
or
* Both
You can look at other moves as conceptually similarly (as a setup move), the only difference being physical space/obstacle vs backstory space:
I’m at this end of the breezeway. The next room is the engineering room where the lightning pillar module is located where I need to tinker to take it out and replace it. But there is a ghost/guard between this end of the breezeway and that end of the breezeway.
So the player will most likely (orthodox) make an Attune/Prowl move to navigate this obstacle, setting up the Tinker move.
I mean there is a contrast between backstory space and physical space. But I don’t think it’s as stark as what you’re proposing. I mean, in effect, every move is a setup move until the win con of the conflict is achieved (like, say, that Tinker move indicated above my have cemented the Score victory)!
Also, Blades’ backstory space is also governed by Flashbacks (as well as Study/Survey). My guess is that Illuminate in the proposed game would likely see a fair bit of usage as a Flashback Action.
<Checks clock and makes sure this quoted my last post>
We seem to be talking past each other. I don't disagree that your formulation above could look like a setup move, but I disagree that it is. Dealing with the ghost is a direct threat, and it's dealt with directly. Play then moves to the next obstacle. A setup move, on the other hand, is made and the same obstacle still exists to be dealt with. To me, a setup move isn't getting past the immediate obstacle to attend to the obstacle at the end, it's doing something to make the immediate obstacle easier to overcome -- it doesn't advance to the next obstacle. This is what I see what I look at your Illuminate action (if that's still the current name). It's couched to suggest that you use it to gain an edge on an immediate obstacle, and doesn't look couched to be well used as a way to overcome an immediate obstacle.
I think the temple traps scene from the end of Indiana Jones and the Last Crusade is a good toy example to look at. As Indy approached each of the three traps, he recalled his teaching and then used those to physically overcome the traps. The way you have it phrased, and the way I understand Spout Lore from DW, the play would look like a Spout Lore check which would establish how a trap works, then a Defy Danger (or other move as appropriate) to leverage that into passing the trap. This is how I see your current Illuminate action phrased out as all -- it's passive and established new facts about the current obstacle, but doesn't directly bypass the obstacle. I think it would be better to have this ability couched in terms of 'do' rather than 'recall', so that the play example could be using Illuminate (and I like Assess better) directly to say that you're using your knowledge of Grail history to get through the trap. One roll, and done.
One of the things I see different about the two above examples is that in Blades, I can always choose to use any Action as a setup, but I can also use it to directly attack the problem. Spout Lore, on the other hand, never (or rarely) directly attacks an obstacle, it's always (or usually) a setup for something else. I think importing this kind of primarily-setup move into the Blades structure does some minor damage to that structure, in that now I have one ability that is distinctly different in use cases from the rest.
Anyway, last from me on the topic.