Why shouldn't a badass with near-infinite amount of history not get his own film?
Hubert wrote a well-argued feature on why a Yoda spin-off film would be a terrible move by Disney. However, despite the points he brought up about Yoda: The First Jedi not being the best move to ensure young Padawans across the world that the Star Wars franchise is in good hands, I feel that a Yoda-centric film would not only be the perfect way to expand upon the universe, but to also introduce the change of status quo of things to come in the galaxy from a long, long time ago.
While I'll be addressing some of Hubert's points, my feelings about Yoda: The First Jedi will diverge towards other areas that Flixist's Favorite Filipino didn't address. Let this serve as a precaution to those wondering why I'm not arguing for more Yaddie. Now then...
Caveat to Escape Yodic I Have Found.
Hubert's first point of discussion is one I actually agree with: Simply put, 90+ minutes of Yoda talking like Yoda would aggravate even the most loyal of Jar Jar Binks supporters. However, since the Star Wars universe, and Yoda's history as a whole, is so open and unexplained, the writers could implement an easy way of getting around "Yodic."
The admittedly cheap option would be to have Yoda speak normally. I know, what a tragedy it would be to take away what makes one of the most iconic characters in Star Wars, well... iconic. But really, explaining Yoda's speech syntax as a product of his age and years as a Jedi Warrior would be a way to get around the speech impediment.
After all, creating a minor retcon like this would allow not only for further fleshing out of Yoda's story, but also opens up a path to future Yoda films (more on that later).
Yoda as the Warrior is Awesome.
Face it, Yoda was a badass in Attack of the Clones and Revenge of the Sith. After the Original Trilogy where Yoda was either on his death bed or hanging on as Luke Skywalker's backpack, it was good to see him unleash some of the skills that helped him become a Jedi Master. Even if the flying squirrel badassness was fueled and influenced more so by fan service rather than what Lucas might have originally envisioned for Yoda, the fact remains that everybody was hyped to see him break out. I know I was when Attack of the Clones hit theaters.
Much like what Hubert pointed out, detractors feel that the bursts of energy went against everything they felt Yoda stood for in the Original Trilogy. However, staying within the context of the narrative, 25 years separate Attack of the Clones from Empire Strikes Back. While that's a paltry number considering Yoda's near-900 years of age, his years in exile on Dagobah aged him dramatically. Thusly, it would make perfect sense to explore Yoda's badass battle past as a Warrior and how certain events helped shape him into the Sage he was mostly known for during the Original Trilogy.
900 Years of Life Allows an Endless Amount of Story Potential.
With the right writers and solid forethought towards a specific direction, a Yoda trilogy could easily be created. As somebody who lives for adaptations of any type, an expansion not only of Yoda's character, but of the Star Wars universe would be great. And let's face it, practically anything associated with the Star Wars name is guaranteed to make money. The issue is whether or not the product is worthy of the money.
In the right hands, Yoda's backstory could, at the bare minimum, function well as a trilogy. Popular opinion might want these films to begin at Day 1 and explore Yoda's origin. However, something with lofty ambitions like a Yoda spin-off would take proper planning and would not be a good idea so early in Disney's takeover of the franchise. Instead, a film focusing somewhere towards Yoda's adolescence would not only be more interesting, but make more sense from a business standpoint.
The Universe Can Be Explored through Yoda's Eyes.
Continuing on in more detail from the previous point, Disney could essentially pull an "Episodes IV-VI/Original Trilogy; Episodes I-III/Prequel Trilogy" with Yoda's backstory if done correctly. If Disney began in the middle of Yoda's life, they could still flesh out his past while still keeping the option open to go even further into his history depending on fan reaction.
Furthermore, Yoda serves as the perfect icon and character for Disney to explore the Star Wars universe's history as a whole due to his longevity, which is a benefit not allowed for other characters, like with the confirmed Han Solo and Boba Fett spin-offs. Essentially, the universe's history as a whole could be explored through a Yoda lens, lending the film expansion a recognizable character they can explore with.
The Mystique Surrounding Yoda Would (and Should) Still Exist.
However, over-saturation of Yoda's history would bastardize the root of what makes Yoda so interesting. I've been arguing for more insight on Yoda, but there's a line that shouldn't be crossed. After all, he was almost 900 when he died; for Disney to even flirt with the idea of covering Yoda's entire life would be blasphemous. With the right team of directors and screenwriters, Yoda's past can be explored without ruining the intrigue.
As Hubert mentioned, the Prequel films were a mess for a number of reasons, but the fundamental problem was in the terrible writing/handling of Anakin Skywalker. The fact remains that a spin-off for any character is only as good as the script.
Why Can't Yoda be the Hero?
Finally, why can't Yoda be the hero? Yes, Episodes I-VI focused on the Father-Son parallels of both Anakin and Luke Skywalker where Yoda played an important supporting role in their upbringing in the Force. However, as with any spin-off, character dynamics are shifted. Does that mean Yoda will be relegated to his own support group of sidekick characters never mentioned before? Possibly, but that's not a definite thing.
As I've previously stated, a spin-off film (or trilogy, as I'd like to imagine) would focus on Yoda's ascendence into becoming the Jedi Master he's known for. Nobody attains such an elevated status without having to partake in the Hero's Journey. In fact, I'd argue that while Yoda was not the Hero in the previous films, he was still a Hero. He's proven himself prior to the events of the films; why not share those stories that helped him become one?