I can't really think of any argument against it either. Here's their argument for him.
* 40-something/can credibly play older – check.
* A super-heroic physique despite a somewhat advanced age (with some acting ability as part of the package) – double-check.
* Commanding screen presence/credible as a military leader – check (at least if you count on-screen experience).
* A personal, outspoken love of comic books and superhero movies – check.
* A box office track record – check-ching.
Johnson has in fact, been called “franchise Viagra”, for his ability to boost the box office performance of film series in which he appears.
One intrepid researcher even put the math to the test and demonstrated what he calls the Dwayne Johnson effect.
And while Johnson wasn’t a magic elixir for G.I Joe’s domestic box office (Retaliation actually generated less North American box office than The Rise of Cobra), the 2013 Johnson-starring follow-up easily outpaced the original globally and it’s the worldwide stage (where the X-Men is not a yet a huge presence) that the Rock could provide the most help.