5. "The Myth Makers"
"The Myth Makers" is another historical, although it's not quite as serious as others on this list. Written by Donald Cotton, "The Myth Makers" was meant to be a more comedic story. It was also designed to be a strange mix of history and myth, with the Doctor even creating the infamous Trojan horse.
The scenes involving the horse and the battle afterwards could be the most challenging to animate. There's a lot that happens in the climax of the story that could drive up the budget.
Beyond that, most of "The Myth Makers" seems to be set in or around the city of Troy, so locations shouldn't be too much of an issue. We can expect one or two changing costumes, at least, especially Vicki. This is her departure story, so it's important that the animated version is handled right.
This story is also significant for introducing short-lived companion Katarina, who's killed off in the very next story, "The Daleks' Master Plan". More than that, the end of this story leads directly into the 12-part epic.
When "The Macra Terror" was released in 2019, the next two stories - "The Faceless Ones" and "The Evil of the Daleks" - were animated in 2020 and 2021. While it's been a few years since "Galaxy 4", I can't help but think that BBC Studios would want to try something similar with "The Myth Makers" and "The Daleks' Master Plan" - animating the setup first before releasing the main event. Either way, I would certainly be excited if an animated version of "The Myth Makers" was announced.