To recap, ATA is a PbtA (Powered by the Apocalypse) game, based on the work of Vincent Baker in "Apocalypse World" and its numerous spin-offs. Rather than character races or classes, called "playbooks", PCs are defined by a mixture of qualities ("I'm Logical, Technical, and Robotic") that provide them with one-off moves or dice bonuses. Characters also come with conditions that hinder one of their five stats: Move, Act, Think, Talk, or Find. Conditions are defined per PC, so (for example) the soldier type can be bloodied and battered, while the less physical nerd type will take more social or psychological damage.
During the session, I ran the group through a combat encounter. They were ambushed by a pack of feral Cat hunters armed with guns, and had to fight them off with a couple of malfunctioning stunners and their own weapons. They won, but took conditions, which was what I was there to test.
The qualities system seems to work as expected. People get dice bonuses for things they're supposed to be good at, or which emphasize their natures. For example, one character didn't get a dice bonus to attack with a stun weapon for his "dangerous" quality, which applies when you "violently engage in combat with somebody". I ruled the stunner wasn't really violent and didn't emphasize the quality, and I think that was the right call.
We had several "success at cost" outcomes during the fight, which is no surprise given PbtA's merciless dice mechanics. Some of the players expressed an interest for more mechanical support for these outcomes. It wasn't enough that I said "your stunner is destroyed" — they were looking for something to write down or put on a sheet to indicate that.
This "tag" concept was intended to soften the impact of taking a condition. Right now, conditions aren't hard to clear, but impose a -2 penalty on actions, which is huge on 2d6. Provisionally, I was thinking of making it like a new mini-condition, and reducing condition penalties to -1, so you'd have five predefined conditions and five "floating" ones. That doesn't feel good or elegant, and I don't think it reflects the intent of the proposed rule.
Overall I think the "classless" style of play worked acceptably well. Players have fewer unique moves available to them, but can create some with custom qualities.
PbtA success is inherently "swingy", and part of the mental shift needed to use these new rules may include accepting that fact. I do think that letting people access more unique moves might offset that feeling, but I'm not sure yet how to accomplish that in a way that doesn't disrupt the quality and advancement system.
I want to run a bit more before I start making more sweeping changes.