What Miguel did was Creepy AF and wrong
I read all of the original Spider-Man 2099 run, and although I don't like Miguel as much as a lot of y'all and I can find him to be a bit of an asshole (I dislike that he's a cheater), I can see that overall he´s a hero.
But what Miguel did in the movie really irked me and felt villainous. And the worst part is that it's written in a way that tries to make us understand where he's coming from / make us simpathize with him. I´m talking about him taking Gabriella´s dead father's place.
I mean, the only way in which I could be cool with this is if Gabriella knew that ATSV's Miguel wasn´t her father. I wouldn´t even mind if to make things easier to explain, Miguel told Gabriella that he was her father´s twin. But taking another man´s place, making a kid feel like you're his father when you're not and probably continuing to talk with that universe's Miguel's friends and family as if nothing had happened feels like an objectively evil thing to do.
I mean, it´s an inherently creepy concept. Imagine that your dad died 15 years ago but you never noticed because someone that looked like him "cosplayed" as your father because he wanted to feel happy. I don´t care if ATSV´s Miguel was a GREAT father to Gabriella, if he didn´t tell her that he wasn´t her biological dad, there´s something truly broken with him.
And yes, I get the narrative need for him to have an origin similar to this so that he had a solid reason to work as Miles' antagonist. However you could have done this in a lot of different ways that didn´t involve cosplaying as a kid's dead father. That just seems wrong to me.
Oh and btw, I just realized while writing this, that what Miguel did is VERY similar to what Kingpin tried to do in ITSV. They both wanted to have a family (in Fisk's case to have it again) to be happy, and they looked for it in the multiverse. Ironically enough, Kingpin´s plan didn´t seem as bad because it didn´t seem like he was replacing anyone.
As Dwight from the office so eloquently said "Identity theft is not a joke Jim! Millions of Americans suffer every year!"