It's no secret at this stage that Obi-Wan Kenobi went through a lot of creative changes during its journey to Disney+ (it was once set to be a movie), but we didn't realise is how big some of them were! According to THR (via SFFGazette.com), Darth Maul was originally set to appear in the series with Ray Park reprising his role from The Phantom Menace!
When writer Hossein Amini was working with director Deborah Chow on Obi-Wan Kenobi, it sounds like the plan was for Maul to be the lead villain. While he died at the hands of "Ben" Kenobi in Star Wars Rebels, the events of this story were obviously set to take place a few years before that clash.
After working with Jon Favreau and Dave Filoni on The Mandalorian, Chow sent them the scripts to see what they thought. Both were concerned Obi-Wan Kenobi was repeating what their show had already done by having the Jedi Master looking after a young sidekick (see: Din Djarin and Grogu). There was no Darth Vader at this point and Maul was going to be one of many hunting down his old foe with Luke, but Favreau and Filoni encourage Chow to "go bigger" with her plans.
As a result, production was paused and a new, older Luke Skywalker was cast (Grant Feely).
The trade notes that Park was on set for pre-production and also involved in early stunt training. One source claims that footage of Maul was shot, but the character was ultimately written out and Filoni stepped in to help figure out how Vader could be brought back alongside the Grand Inquisitor from his Star Wars Rebels series. These plans for Maul also likely contradicted much of what he did there and in The Clone Wars, so it's no wonder the former Sith Lord failed to make the final cut.
It's hard not to get excited over the prospect of a series featuring Maul chasing down Obi-Wan given their history, but Vader's return does feel like a much bigger deal. Hopefully, there is still a place for a live-action take on the villain, especially after what we saw at the end of Solo: A Star Wars Story.