I've been paying special attention to how the series depicts fanservice. For one, like you say, Momo is never oogled by the framing despite her outfit. And while it still is a fanservicey outfit, it has a better justification than most, since Momo is indeed going to pull giant things out of her body. It's also treated so matter of factly by while done. And the other girls outfits are just not that fanservicy, other than Pinky's I guess, but I don't really feel the 'camera' itself leers at the girls, which alone makes a big difference.
Other than that, it's not THAT much different from other shonen. Main characters are better than average, but side characters, I worry there will be a discrepency. The Shapeshifting girl of recent chapters being a prime example. MHA has proven itself to be atleast someone clever with this, so I'm hoping that he'll do something clever with her instead of her just being naked for no reason. It's probably the most blatant and straightforward example of it thus far. But Midnight has been around for a long time now, and we still don't have a real answer to why she titillates, especially since it's not related to her quirk.
Plus, we have stuff like the springs episode, and a scene while the girls were in the girls locker room. A lot of it is perpetuated by Grape Juice, who usually gets his comeuppence BEFORE he gets to see anything, which is atleast variation since most gags like this are after the pervert sexually harasses them...but the viewer still gets to get a view, so the effect is basically accomplished. It would actually be kind of clever if we didn't get to see the girls and our avatar in trying to do so is just punished.
That said, here's whats in it's favor:
1. not all women are depicted in sexual terms. In fact, most of the main characters, including Uravity, are dressed normally for their setting. That's important. Without it, Momo's excuse would be just that, an excuse, but since not all female characters have that kind of outfit, I can much more legitimately buy that it's something she needs for her powers.
2. The fanservice they do have doesn't come at their expense. The viewer still gets the male gaze, but I can't think of an instance where we get the male gaze at the expense of the girls state of mind. The closest I think is when Grape juice, the prick, groped Tsuyu, but that came off more as a gag than anything. I'm much more comfortable with the camera panning over to the girls in the hotsprings just relaxing, which is the normal social thing they should be doing anyway, than our POV follows a guy who is just getting a peeking and they have panic and cover up. Still not good, but better.
3. The fanservice doesn't get in the way of character moments. With the female characters, we get moments of fanservice inbetween getting to know them all as characters. For many other series, including the first chapter of Illegals, I feel it's the inverse.
Honestly, I struggle with this. Is all fanservice bad? I don't think there's anything inherently wrong with liking a character sexually, nor do I think there is anything wrong with having a moment where the viewer is titillated to. Attraction to others is part of life and why shouldn't it be part of entertainment?
I guess my basic standards come down to if the work respects the character as a character first and foremost and then gives some fanservice following that (I feel MHA does this fairly well for the most part, but it's hard to see that as much with characters like Midnight and Shapeshifting girl since that is how we are introduced to them) and I wish for it to be a bit more evenly spread out. I have no attraction to men, but I'd feel better if there was an element of female gaze in most works, just to be more inclusive. There are some feminist that argue that playing toward fanservice to the other way doesn't solve the problem, but I disagree, and I think we'd feel a whole lot less creepy about oogling fictional characters if women/gay men were free to oogle them beside us.