One thing that just seems to be true regardless of map is that maintenance doesn't have air vents or scrubbers. I believe that, both from a lore and from a gameplay POV, this should change.
Let me first talk from a gameplay POV:
What is the main purpose of vents? Is it supplying the station with air? While that is one of their functions, I would argue it is not the main one. Crew don't use up enough air for replacement to be needed. If it was just about recycling air and filling maints up after a leak, then adding vents to maints would not make much sense. The handful of times where maint needs to be filled with fresh air or scrubbed, portable tanks and scrubbers can be used. But in my opinion, the main reason for vents to exist is in fact ventcrawling.
A lot of rounds end up spawning either a mouse-blob, terrors or xenos (though rip for xenos for now), on top of more rare ventcrawlers like antag atmos techs or morphs. The vent network is their primary method of movement. However, those event antags all want a quiet place out of view to build up in. This forces them to go to the handful of places in maintenance that do have vents and are thus accessible, namely turbine or chapel electrical maint.
The fact that maints don't have vents sharply constrains those antagonists, especially at the very start, forcing the evolution of a strong meta by leaving only a handful of viable nest/blob locations. Even after the start, it is not rare to see terror spiders stuck in maint rooms behind doors they can't force open, where vents would be a natural way for them to spread and get around.
Another factor that was brought to my attention is headcrabs. Headcrab nests get spawned somewhere in maintenance, nobody finds them, they build up a shitton of crabs that are all trapped in one tiny room to be unleashed on whoever is unlucky enough to open the door. If maintenance had vents, we could make headcrabs ventcrawlers (if they aren't already), which is a very headcrabby way for them to spread around.
You could argue this would make those antagonists more powerful, especially in maintenance, since a xeno hunter or terror spider could be lurking in a vent in the dark. IMO, that would even be desirable, making maintenance a great deal scarier than it currently is. The biohazard invading the station having an advantage in maintenance seems appropriate to me. Since maintenance vents are in less frequented areas, they should also have a tendency to not get welded as much, leaving biohazards a way out of a mostly welded network.
Secondly, let's talk from a lore POV:
First, let me say that I firmly believe gameplay and balance concerns should be more important than lore. With that out of the way, are there arguments for or against vents in maintenance? You could say that maintenance is not a proper part of the station, not designed to be livable or comfortable and that's the reason why it doesn't have any ventilation.
However, not having areas on your space station get any fresh air, ever would be an incredible safety risk and liability. Secondly, there's areas of the station proper only accessible via maint, so there's an expectation that some people need to go there. Third, if maint is supposed to be this inhospitable, why does it have some lights? And lastly, there are areas of maintenance that are flavoured as former station parts that were abandoned. Areas like old bar, old diner and so on are supposed to have once been normal rooms. Why, then, did someone go through all the trouble of ripping out their vents and scrubbers, instead of just turning them off or whatever?
My proposal
So, what exactly do I propose? I don't think maintenance should have anywhere close to the vent and scrubber density that the proper station gets. However, there should be some scrubbers and vents added in choice locations where they can cover a fairly large area, as well as in locations that are formerly normal rooms like old bar. That should give blobs and spiders more choice in starting location, lessening the meta-factor.