Matt Reeves' highly-anticipated, Robert Pattinson-starring The Batman is just under a year away. It'll be the biggest theatrical event, certainly for DC, in 2022, and the recent teaser trailer propelled hype to new heights. It's only composed of clips from 25-30 percent of the film, but gave fans a fascinating look at an adaptation of Batman not yet scene on the big screen. Part of that, coupled with interviews from Reeves and Pattinson themselves, is because it's starting to look like the film might actually get an R-rating.
This would make The Batman the first theatrically-released, live-action movie about the superhero to get an R. While many fans salivate at the prospect of this, and understandably so, it could backfire if mishandled. Given Matt Reeves is directing and also a writer, there's a strong chance they'll pull an R-rating off effectively/tastefully, but here are reasons it could go well or poorly.
R: Joker's Success
Likely the first and most obvious reason pointing to how an R-rated, live-action Batman movie could prove successful is by looking at the success of last year's Joker. It proved to be well-received critically and massively successful commercially, becoming the highest grossing R-rated film (over $1 billion).
It's a Batman movie only by association and they're different characters, but given their warped, obsessive relationship and, while not the same, being two sides of the same insane coin, Joker's success could be the gateway for a directly-related Batman movie to succeed. The potential rewards are greater, as this time it'll literally be about Batman, which should have even more appeal.
PG-13: A 'Hard' PG-13 Suffices
With live-action Batman movies, PG-13's proven to be plenty for dark, gritty, grounded, and profound takes on the character. Christopher Nolan's The Dark Knight Trilogy, and The Dark Knight namely, effectively used the PG-13 label to be as serious as necessary without crossing any heavy-duty boundaries in terms of themes and the like.
The Dark Knight did well using a 'hard' PG-13 rating in terms of themes and overall tone, and there was minimal blood at best, yet no one complained. PG-13 doesn't mean Batman movies are forced to adopt/confine itself to the tone of an MCU movie.
R: Perfect For Noir/Mystery
To those who have been following updates from the creative team since before the first trailer dropped, it's clear that The Batman fully intends to delve harder into noir and mystery aspects of Batman and his stories, which is deeply exciting. This could, properly and finally, give us a live-action, theatrical iteration that fulfills the superhero's epithet of World's Greatest Detective and Dark Knight instead of only the latter.
The trailer makes it clearer with depicting a Riddler--seemingly poised to revolutionize the supervillain with Paul Dano like Heath Ledger masterfully with Joker--portrayed as a "Zodiac Killer" or Se7en antagonist. An R-rating could beautifully use this character to his potential to flesh him and the plot out as a proper noir/detective-thriller that gives Batman a compelling physical and intellectual challenge.
PG-13: R Would Alienate Certain Demographics
A more obvious point in favor of sticking to PG-13 is that an R-rating would alienate part of the younger crowd. This is more about commercial success and not necessarily a question of quality. Given movie theaters' current state of limbo, shattering the box office with a great, R-rated Batman movie in the same vein as Joker is not at all guaranteed.
Thus, alienating younger audiences with an R, even with the film shaping up great, could be crippling the profits to an extent. PG-13 would ensure the max number of seats filled, which will be crucial in the event that theaters are still in turmoil in 2022.
R: Psychological Elements
Among the big thematic appeals of The Batman is it'll intend to explore the inner workings of Bruce Wayne's mind, particularly his "humanity" as the man behind the mantle. Given that Reeves revealed Ego will be a major comic book-influence on the movie, an R-rating might be a great way to ensure maximum (tastefully-done) creative liberties in exploring the nitty-gritty aspects of the character's psychology.
PG-13 could accomplish this well also, as The Dark Knight Trilogy proved, but a deep dive into Bruce's head in an R-rated, noir/mystery-thriller is a mouth-watering opportunity.
PG-13: Gratuitous Violence
One of the most thrilling parts of the trailer was the vicious beat-down Batman delivered to a clown-inspired (Joker?) thug. But the more interesting part underneath is that, given the efficient and calculated precision of the "fight," is that we'll likely finally see a Batman that can convince fans he's a master-level, hand-to-hand combatant. Audiences saw this once in the warehouse fight in Batman v Superman.
Praise aside, what could threaten the movie if this is R-rated is if the violence potentially being gratuitous. Fans don't need to see a Batman movie that puts too many overwhelming beatdowns that make Batman look completely unlikeable/irredeemable/unrelatable, as that was the bulk of the backlash from BvS. Likewise, no one needs to see him kill again, as he's bafflingly done in several past movies, Nolan/Bale and Burton/Keaton included. But with Reeves behind this and Ego as influence, killing should--finally--be off the table.
R: Diving Into Corruption
The plot's central premise is the deep-rooted corruption plaguing, eating away at Gotham City's wealth and spirit, as Batman famously said in Year One. With that, it'll explore Bruce Wayne, a man born into wealth, that has been forced to see how filthy the city is when a piece of that sickness robbed him of his parents, and how that filth affects everyone. The trailer itself promises to bring revelations that'll expose the true magnitude and scope of said corruption, as well as how Bruce is in the thick of it--unknowingly.
With a premise that tantalizing, an R-rating could get the most of what the story can tell and what it can show. It could take opportunity to free itself from PG-13 to make some resonant commentary on the extents of corruption in its various facets, much like so many crime-thrillers.
PG-13: Avoiding Post-Returns Reactions
Burton/Keaton's films were certainly critical and commercial successes. Batman (1989) set the world ablaze for the places the character can go in tone and theme--and superheroes in general--and deliver something great.
Despite the positive critical reception of Batman Returns (1992), audiences were concerned it was veering too far into gothic-horror territory. After all, these were unabashed Tim Burton movies. What resulted were two sequels that went harder to Silver-Age camp to the point where the live-action franchise died for nearly a decade. Reeves and co. should be careful not to lead the franchise into a similar cycle.
R: Daredevil Proved It Can Be Done
Memes/superficial comparisons aside from The Batman and the MCU's Daredevil from the screentest, the latter proved a mature-rated, live-action superhero adaptation can be done. It wasn't a film or series of films, but Daredevil was a critical success even in its weakest season, masterfully reviving the superhero in the live-action arena.
Daredevil had the benefit of being a show and not a movie(s), but it nonetheless provided the blueprint for crafting an excellent gritty, grounded superhero story. Particularly so for exploring the strengths and vulnerabilities, physically and mentally, for fascinating characters like Matt Murdock/Daredevil and Bruce Wayne/Batman.
PG-13: Leave Mature Ratings To Supplementary Content
DC is set to expand and compete with the Marvel by embarking on a mass multiverse, rather than sticking to a single universe with the DCEU films. Everything is in connected, regardless of universe, but as much as they want to be, similar to the DC Black Label comics. WB/DC/Reeves can do plenty with PG-13, but still get to explore R-level content with supplemental/complementary content.
Reeves is building a Batman universe, which will include a GCPD HBO series. These kinds of productions can afford to let the films stay in PG-13, as the creative liberties of TV--and on HBO no less--are more lax.