I wouldn't be too worried about that. The super powers would definitely set him above the Robin level for sure. Clark would prove himself equal by the end of the movie I bet.
That's the problem. It's a lose/lose situation. If you really play up the "older and wiser" angle, you will make Superman look more like a Robin. If they become equals at the end, you will make Batman look bad. Why does Batman need an entire decade of experience to be
equal to a young rookie Superman that just started out? That's really insulting to Batman IMO (I know it technically can't be since Batman is not a real person but you get my point). Superman and Batman were equals from around the very beginning of their careers, which they started at around the same time, and then they grew together up to their weary/tired/seasoned years and they were
still equals even then.
If Batman needs to have 10 years of being older and of more experience, what does that say about Superman in 10 years from MOS? The
current Batman would be useless to him. By the logic of an "older/weary/tired" Batman being an
equal to a young rookie Superman, the
only reason why he is on par with him is due to the age gap. And I find that really disrespectful to the character of Batman.
As for Batman being older and experienced, it should be considered a Benefit. Batman should be given something to set himself apart from the other god-like heroes of the Justice League, who are all probably Superman's level of being a rookie, age and experience in fighting bad guys, and being a detective etc seems like the best. Tired and weary could simply mean he's fed up and wants to retire, until a young upstart by the name of Superman inspires him to keep up the good fight.
You don't have to give Batman anything to set him apart from the rest; he already has it. The genius intellect and detective skills are not a product of him doing this for so many years but of his motivations and mental training he received
prior to becoming Batman. Since the Modern Age of superheroes started in the DC universe, Batman has
always been the smartest man in the room despite being the same age as Superman and the rest.
Again, it goes back to the idea that the only reason Batman can survive on the JL is due to the age gap.
Look at it like this, which Batman cartoon do you prefer?
The young Batman who's a couple of years into his career from "The Batman" animated series
or
The older Batman from "Batman: TAS" who clearly has been doing it longer
No offense, but you've brought a horrible analogy.
Batman: TAS is a show that gave it its all while
The Batman was an intentionally dumbed down & poorly written Batman show that made Batman look like an idiot half the time. There are
so many problems that show has that it's ridiculous, and a younger Batman is not one of those problems. If you want to argue that a young Batman simply can't work in the JL, you should source a Batman product that at least put half an effort into itself, which
The Batman didn't do.
Plus, Batman is not that old in
Batman: TAS. In fact, he is only a couple of years older than Batman was in
The Batman (who was around 27/28). TAS' Batman is somewhere in his late 20's to early 30's; he just started his career as Batman a few years earlier than Comic Book Batman did and that gives off the impression that he is older than he really is. Plus, TAS Batman was still around the same age as TAS Superman. If there was an age gap between them, it would be very small thus the twin-brotherly relationship was still there.
Not the same thing as Batfleck who is older than Superman by 10 years
and has more experience than him by 10 years.
To let you know, I have zero problems with an older more seasoned Batman. In fact, it is the type of Batman I prefer. I grew up mainly with that Batman my whole life. What I do have a problem with is making Superman or Batman older than the other one by around a two-digit number. I wouldn't mind the idea of an older Batman if this universe's Superman was older too. But since this universe's Superman is young, Batman should also be younger even if he's been doing this for a few years already.