I feel I should clarify a couple abstractions I've made here that aren't necessarily critical but they are relevant.
You aren't forcing anyone to move out from their families and live with you. Your housing limit is a bit of an abstraction based on what portion of girls aren't living with their families and would otherwise be homeless. (This is far higher amongst meguca than general population though simply because of the nature of people Kyuubey selects.) The ones that have families still live with their families.
This explains why housing gives a significantly larger boost to population than the unit would imply. For instance a normal house shouldn't be able to hold 25 people, but I figure it's more along the lines of 60%ish of your girls actually living there (noticeably higher amongst those you started with actually). This frees me from having to track who is specifically living with your group and who is living with their families, and made housing costs much more reasonable for you in this start up phase.
So any girls that you meet uncontracted and that become magical girls don't have to live in your cramped apartments they'll keep living with their families unless they don't want to. So your apartments aren't quite as cramped as the numbers imply. Though in down time there is a lot of hanging out together at these apartments simply because the girls are all friends driven together by mutual circumstance.
Also you don't actually have one apartment. You have a few of them, I think I put it down somewhere as 3 or maybe it was 4. (Not counting Mami's apartment.)
You aren't actually operating at any negative on combat at this point. Any negative effect from being safer is far countered by the simple fact that they gain more experience by living longer. Though some groups will have combat bonuses your raw numbers give you something of an advantage at this point.
Also it may be worthwhile at this point to reveal something. You'll likely have noticed at some point that pack hunting specifies "Death is significantly less likely" which is not redundant with the reduced casualty chance. 20% of casualties from pack hunting are deaths; 50% of casualties from solo hunting are deaths. This is to represent the fact that if you take an injury like losing a leg and you're alone, the enemy is very likely to finish you off. If you lose a leg with a group, your other squad mates will try to protect you and pull you out of the combat zone. I probably shouldn't have revealed this and just let it be revealed over time, but it's probably something Mami would recognize on her own.
Okay, nice.
The bit about injury vs death, well I thought that was pretty obvious. So I don't think you gave away the game there.