If this was a Filoni show, I'd be wondering if his fanaticism would lead him into recruitment as an Inquisitor, but I don't think that would fit the tone of Andor. I'm just not sure where there is for him to go. The ISB doesn't seem at all likely to recruit loose-cannon fanatics, even loyal ones. But I can't quite see his vision of the Empire being so broken that he becomes a rebel instead, either. If I had to guess, it would be that he screws things up one last time (to our protagonists advantage) and then dies or goes to prison - having Syril ruin the ISB's operation lets them remain dangerously effective antagonists for future seasons, while giving the protagonists a chance to run that makes sense.