I hc wash and south (and by proxy, north) as all being ODSTs prior to pfl and one thing I really like about hcing them as such is that it adds another layer of depth to why they were all chosen to be a part of the recovery force.

ODSTs are a special forces unit within the marines, and they're generally used as force amplifiers and in high risk or sensitive operations. two such scenarios include the recovery or recapture of personal and high level assets behind enemy lines, as well as deep reconnaissance and intelligence gathering. ODSTs are also used in politically sensitive operations, which pfl was following the crash of the moi.

so basically, who better to be on the recovery force than former ODSTs who already have a background doing the kind of work that would need to be done?

this also adds to some of the tension between north and south as well imo, as while they're a great team who are capable of working together they clearly have two very different skillsets—south is not portrayed as someone who has the patience necessary for long reconnaissance missions, and part of the reason why team b failed so spectacularly is because two snipers and an intelligence operative are not a good choice for a smash and grab mission. had north been replaced with south things would've probably went way better for them, because south is actually fairly similar to wash in her "get in, get it done, get out" mentality, though where wash comes off as more methodical and is willing to take that "wait and see" approach, south throws caution to the wind and has a "we'll cross that bridge when we get there" approach.

this is probably why wash and south were (on paper at least) going to get eta and iota—south would've benefited greatly from having an ai that was afraid and anxious as it would force her to slow down and think things through more, and wash getting an ai that was happy and cheerful would force him to loosen up a bit and be less high-strung and serious.