I don't know "stalker" fiction. If I have time in the next two weeks I'll read up on some summations. But as it stands, I haven't had the time to devote to this concept-wise, but from your last comment, I want to go ahead and say this:
The Ruin Runner is about finding stuff in big trash piles, ruins, or hazardous places and then running with the valuable stuff back to people that can use them. Even juryrigging is based around this concept, they just have watched enough people use their scrap that they short-of kind-of know how it works and can try to do it too.
It is a pretty evocative playbook, but it really should be stressed that one of the most fundamental aspects of the playbook, and its charm, is the role it places within the narrative. Its about the fact they're constantly doing stuff for other people. They're good at getting places and daring trouble along the way, but they essentially need someone else there to use their skill set and give them a place. They dont know how to do it alone.
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Again I hadn't read your playbook all that thoroughly, so feel free to dismiss this, but. You seem to have taken a lot of the scrap out of the playbook and put in the tech and this know-how. I worry that it provides an already independent playbook more of the social role that involves them doing these things for themselves, rather then someone else.
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If the focus is about finding strange weird things, maybe you should consider embracing that totally.
Maybe: Drop Scavenger. Use Somewhere out there as the primary playbook move, design it so that it doesn't need a roll. They find stuff like a savvy head works on tech. Literally, its a narrative implication of the class that they can find something that does X. So lets skip the part where X might not be out there, and just give them runner the conditions they'll need to achieve to get X. The work is getting there, just like the savvy heads work is making the thing. That would start you off with a pretty evocative move.
Drop Jury Rigging, this doesn't seem as much of a USE ALL THE TRASH goal, it seems more of a use this weird ass tech. Replace it with a Weird move. I'm not exactly sold on copying the text from anything else, I think you could probably narratively define out you want this guy to interact with the specific loot he's pulling out of the fallen world, and then say what happens on a hit vs a miss, and go from there. I'd personally think that something that combines a theme specific trigger with a mix of jury-rig + the savvy heads read an object. Think about how this move relates to the social placement of the class. If he is just a speced up delivery man then maybe jury-rigging is best after all, but if he is some sleuth backed by tech, maybe there's something more potent he could be using the stuff for.
Packrat is fine. Though If you do start to make this into it's own playbook, it might find a place alongside ruin runner by the end. At which point you'll not want shared moves. I guess a short paragraph of who this guy is and what he does with what he finds/ what specifically he is looking for, would setup that conversation best.
In the Zone, makes me think that this playbook is trying too hard to keep ruin runner alive, and not shifting into where it seems it wants to be. There's not a lot of direct synergy with the other moves as they stand.
Pathfinder, really, I think the Somewhere out There actually does this better. I think perhaps being able to interact with the landscape (as a thing with wants and needs) might make In the Zone a bit more interesting as well, which would also help fill the role this seems to be gunning for.
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+2 Ongoing can be a sure, I'm a fan of you, never fail is fine! But I personally hate it when the players knows for a fact that their +5 stat role hits a partial 7-9 result on a snakeeyes role. I feel that anything that lets this occur is fundamentally removing the realism of the world and thus: is not actually being a fan of the characters. Well once or twice might be fine, but definitely not continuously until the set conditions are fulfilled.