king of rarepair hell

I think he's very jealous of Defensor when First Aid is attached, and he mostly wants to get First Aid detached so he can Reclaim His Property. Defensor likely feels a similar way, enhanced by the fact that the Protectobots as a gestalt are very close to one another and none of them would want to see First Aid in the hands of a Decepticon, whether that Decepticon likes him or not. Cue a lot of violent combiner clashing.

I've been thinking SO MUCH about the next part. We are talking G1, so whacky hijinks must ensue. The Decepticons initially just steal a regular ambulance, and Bruticus realises it's not alive as soon as he gets his hands on it. Insert tantrum. Their next step is trying to pass off a Decepticon as First Aid; Dead End gets painted red and white because he's just about the right shape and he's part of a gestalt and maybe that's what Bruticus find so appealing. This one takes a bit longer to work out: probably a few days before the false First Aid is revealed because poor Dead End got dropped in a river and all his paint washed off or something. Even bigger tantrum.

The Decepticons probably get desperate enough that they nab another Earth ambulance, smuggle it to Vector Sigma, and have it brought to life in the hopes that the resulting Decepticon will be a suitable distraction for Bruticus. The poor bot gets called Last Aid, and his only purpose in life is to be a cute little boyfriend. He's a triple changer and turns into an ambulance and a left arm, but he doesn't have a gestalt to bond too.

Last Aid ends up being pretty much Shattered Glass First Aid: he's a classic evil clone, obsessed with First Aid, the Protectobots, and the Combaticons. There's a bunch of nonsense in having to ensure the Combaticons don't know that Last Aid isn't really First Aid, because Bruticus mustn't know. Last Aid gets mostly ignored and his only assigned mission is "keep Bruticus happy". He is absolutely venomous at this being the purpose of his life; he hates the Decepticons and Bruticus. For a while he probably tries to manipulate Bruticus into idk, stomping on the real First Aid so he can take his place, turns up to cause havoc in the Protectobot base, and is generally a funky evil little guy with a kind of sad backstory (but also he is so very evil).

I don't think Last Aid is very nice to Bruticus, and that's probably what eventually reveals the ploy. Maybe he hurts Bruticus somehow and First Aid finds Bruticus injured, and being First Aid he can't not help, but this giant combiner is kind of shying away from him and waiting to get smacked again. Maybe this is the first moment where First Aid isn't scared of Bruticus, and Bruticus learns what being treated gently is like.