You could have a bunch of films leading up to Doom with tie ins to him with various lesser villains, maybe introduce him part through where he loses, then have a film or 2 where he wins which then transitions into a greater threat where he becomes a hero and we grow to like him but then he turns evil again with altruistic motives like Thanos, there's enough comic material out there for him to be a greater villain than Thanos and we could actually get a full Marvel universe complete with the F4 and X-Men
I'm not saying they can't do that route, but it also puts believability at risk. Where you have a Human, Super Genius and Technosorcery capability or not, is supposed to be able to be a greater threat than the guy who slaughtered half a Universe (who also has a background in being "superior" to a Human being a Titan and then being able to wield the Infinity Gauntlet). Otherwise, it'll come to a point where it's like Independance Day, where you hack and upload a "human" computer virus to a Biomechanical Mothership with an Apple Laptop. Whilst it's OK in that respect somewhat, it'll start to glare when a Human with no capability to be that big a threat, now presents themselves as one.
If I were in the MCU, I'd fast track Galactus into the next phase, have them become the next major threat for everyone. Have the Fantastic Four have their Solo origin film the year before the big crossover with a small cameo by Doom which shows their entry into their "suit" from a situation caused by the FF, and then on the year of the crossover, have one more film but have Doom be a hero to his people by stopping a Herald over his land after a difficult struggle, possible needing a further sacrifice from him (and his people who loves him) showing how weak he really is in comparison. But after the crossover and Galactus is stopped (for now), the part of the computer core of Taa II falls from orbit and lands in Latveria after taking a battering from numerous heroes, where it continues its job to serve and grants its user - Doom, the mysteries of the Cosmos. Increasing his standing as a threat through his knowledge gained from Galactus' computer, whilst still remaining Human.
THEN, I think in the phase after that, can you truly have Doom as a GREAT villain. As both a Human who is flawed in the first place (egocentric), whilst given the knowledge of a God. Which gives them the believability of being able to outthink everyone and from their gained knowledge, be a greater threat than even possibly Thanos, whilst still being Human and flawed. Which can then be explored as necessary in required Disney+ series or movies.
That's just my thoughts on the matter.
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