2. "The Smugglers"
When I began writing this article, the First Doctor story "The Smugglers" was initially much lower down my list. Mainly because it's a historical story, which can be much more expensive to animate.
But after thinking about it, "The Smugglers" sounds like a story that could be relatively simple to adapt to animation, especially compared to other historicals like "Marco Polo" or "The Crusade". For one thing, while the cast isn't small, it's not too large, either. The setting of 17th century Cornwall also sounds like a simple and straightforward setting to animate.
There's one more reason why I think this story is likely to be animated, though. And that's based on the more recent animated releases.
I mentioned earlier how three consecutive Troughton stories were animated from 2019 to 2021. I also mentioned that a similar approach could be taken from "Galaxy 4" onwards. However, it has admittedly been a few years since "Galaxy 4" was released, and a likelier option would be from Hartnell's later stories. Especially after the announcement of "The Savages" being animated.
Last year, "The Celestial Toymaker" was finally animated. This wasn't too much of a surprise, especially considering the titular villain's return in "The Giggle" last year. The next story is "The Gunfighters", which won't get the animated treatment as all four episodes survive. The story after this, however? "The Savages".
If "The Smugglers" was animated, this would present a nice clear line of stories - from "The Ark" to "The Power of the Daleks" - that fans can watch in order, via a nice mix of live-action and animation. There'd still be clear gaps, particularly in the first half of Season 3, but it would still be incredibly satisfying for Whovians to be able to watch so many '60s stories in consecutive order.
Even better is that if "The Highlanders" were animated, that line of stories would be considerably longer, stretching until the end of Season 5. Speaking of which...