Would Dominus Ambus still join the DJD if he were never get turned into the Pet 🤔?
Didn't he join as a spy Before getting caught and being turned into the Pet??
In the circumstance he's never Domesticated, I see a few different juicy opportunities depending on how you go about his time as a spy having affected him, and arguably there's tragedy both in him staying and in him leaving.
Imo the most fucked up scenario there would be if he had been revealed but fully defected afterwards and pleaded that he was a real decepticon now, and I like to think this'd probably happen in the circumstance that Tarn decides that Vos is too useful to kill but needed "saving" to fully settle into the persona. (In my mind this probably involves brainwashing, but godd it'd be horrible if not though. If Agent 113 had fully decided he'd rather be Vos the decepticon rather than Dominus the autobot, and had grown to enjoy the torture-murder even.)
I see an interesting case for if Dominus stays as Vos but is never revealed. Of the spy whose persona is still a persona but he realizes he doesn't have a life to go back home to and he's accidentally made a life here. Of the rest not knowing his past where he knows, but the longing for companionship in his spark ultimately wins out against his mission. He stops sending out information for his handlers. He scrapes off the hidden autobot badge underneath the loadbearing armor. The guilt hurts less a little bit each day, until it stops hurting entirely. Vos hopes Rewind found someone better than him in the end, and that he never comes looking for him.
The situation in where he leaves and his mission succeeds without him being caught is arguably the least psychologically damaging scenario here, but wowww is there such nice cruel scenes in Dominus joining up with the Lost Light after his infiltration of the Decepticon Justice Division. The inital panic, the debriefings, the unofficial questions, the realization that people were still looking for him after he went undercover, the thorough destruction of not only his life as Vos but also his life as Dominus Ambus before it, lots of fun opportunities here.