It turns out that Thanos originally had a much bigger role in Guardians of the Galaxy. The Guardians series remains very popular, and the third film is reportedly going to start filming in 2020.
The journey of Thanos in the MCU is interesting to look at. The villain was shown during the post-credits sequence of The Avengers. He would appear two years later during Guardians of the Galaxy, where he had Ronan the Accuser acquire an artifact containing an Infinity Stone. He appeared after the credits of Avengers: Age of Ultron, wielding the Gauntlet. He finally made his presence known in Avengers: Infinity War, where he snapped half the universe's life out of existence. (Interestingly, an early draft was to have Thanos narrate the events of Infinity War.) He returns in Avengers: Endgame for another stand against Earth's Mightiest Heroes. Some may agree that the build-up for Thanos was effective, while others might say it took too long for Thanos to actually do something. So, it's interesting to consider how an expanded role in Guardians of the Galaxy would have effected things in the long run.
In an interview with Looper, Charlie Wen, the former visual development head for Marvel Studios, revealed that the original plan was to have Thanos play a more significant role in Guardians of the Galaxy. Ronan's role would have been diminished. "Thanos' role would have been significantly larger," explained Wen. "We would have seen some of the relationship [and] tensions play out between him and his kids [...] Ronan's role would have decreased, with Thanos taking on more." Wen would also reveal that Thanos was going to be cut completely from Guardians. At the last second, it was decided Thanos would have a role, albeit smaller. Wen had to quickly design the villain and iconic throne in just a couple of days.
It's very interesting to consider how the MCU would have been effected by an increased presence of Thanos. One can subscribe to the thought that more Thanos is good. After all, many expected to see him do something sooner than later when he was revealed at the end of The Avengers. On the other hand, one can argue that the slow build-up helped to establish the character as a secret mastermind, thus making his appearance in Infinity War all the more effective.
For Guardians, more Thanos could have potentially made the film even better than it already was. At the same time however, there's a chance he would have stolen the show from everyone, including the new antagonist. If Ronan had a smaller role in the film, the Accuser would have probably been even more forgettable for the many who didn't find him interesting. Thanos' screen time in Guardians of the Galaxy is arguably just long enough to feel his presence, while also not stealing the show from other characters.
Source: Looper
