But the problem of giving him an OP ability is that it becomes an easy solution to future problems, and there'd be no point of giving him an OP ability if he's not gonna use it(unless author is just gonna keep on putting things like "the enemy has a cancelling field" or things like that).
The times that he needs to be saved is all the times author introduced a new character(s)... it's like it's the author's easiest way of adding new people to the cast... also the amount of times he needed saving is probably less or equal to the amounts of time he has saved others by using "current era products". So that is a moot point(kinda).
Also applies to him not gaining an OP ability it wouldn't matter.
He already has a reason for not choosing it though, he's content with being a merchant and not an adventurer. And he knows what the negative effects of adventuring is with Aina's situation and Patty's situation. I personally don't think those are "stupid reasons".
The author could've easily just added the option just to enforce that MC isn't like the other isekai MC's with their OP abilities and whatnot... just as the author gave the option for MC to choose to have and OP ability, he did also gave the option for MC to choose to not take it.
All in all I wouldn't mind if MC did get an OP ability, I just feel like it'll be going against what the story was set to be.
Your arguments don't make sense.
The issue is that even if he gains the powers, it doesn't need to change anything, because the author can instead make problems power can't solve instead. In fact, most of the problems he had were ones that power couldn't solve with just ONE not being the case.
And if there are too many problems that violence could solve, then this would be way too much like other Isekai stories.
And if he ignores the existence of the problems power could solve, then it's his fault.
If he and Aina are in danger and he didn't have the power to protect her, he caused her to suffer because he rejected power to protect her.
Also, saying that he's not like the other MC's is stupid... because there are also MC's without power... if the only reason you have your character make a bad choice is to be different, than that's bad writing.
And having power doesn't mean he NEEDS to be an adventurer... it's just power to defend himself and his loved ones.
I'm content with being an merchant so I don't want to be an adventurer is not a good argument, because the power would be for self defense and protecting his loved ones. As a merchant, that would be useful, and if he could boost his physical abilities, that would be more convenient for him.
He already faced people trying to harm his loved ones before and even danger to his own life. So avoiding a good self protection measure for no reason makes little since.
The moment you give a solution to a problem and you don't use it for no reason, from that moment on, that problem becomes stupid because it's a problem that shouldn't exist.
That's just irresponsible and dumb.