It not only isn't necessary, it makes it marginally more difficult for those who use your helper squad. The helper squad is used as-is, without excluding non-nation members. It only excludes non-nation girls from the four teams the user puts up. So keep putting your best girls in your helper squad no matter where they're from, because those who use it won't be able to have all of their best girls.

(Should also be noted that at least for now, none of this makes any difference since the maps we have now are so easy.)