
Let's see...if MC was to make himself a "personal crew" of badasses...
Marcus is either retired MARSOC or FORECON (can't remember which) so he's good to go. Something to keep in mind though, is he has a wife and kids. They're going to be his priority, and rightfully so, so we don't know how enthusiastically he'll be charging the wire so-to-speak.
Spike was in the MC's unit as a machinegunner if I remember correctly. I don't know if we'll be able to get him a 240B, but I'll assume he's probably taken an assaulter course or 2 since he was in the 75th, so he's good to go as well.
Kira is a vet, but was regular army, I believe (MC rescued her convoy or something?). Either way she's been in the shit and is likely rock-solid.
Ashley's older brother is a retired vet and has been mentioned a few times so there's a chance he may show up.
That's a pretty solid group of 5 with the MC. Now they just need some actual gear.
As for "Katana" - I like your idea of her being there to "rescue" / protect her. I dunno, though. She showed up alone and on a bike. She's not rescuing anyone like that. She needs a means of transportation to get her out of there. A "protector" on the other hand...sure, if she had to get there fast, then I could see it, but again, the ideal way would be to get the target out of there, and you need a different vehicle for that and you can't just assume you'd find one at your destination.
Now, an assassin...that would make sense. And if she is, then this bodes extremely ill for Eito and Tomoko

(), and that's before they lost her target.