Mercs for Hire

[Lochar]

Is there some certain schedule for which merc shows up where? After a nasty battle with the rebel camp, I lost 1 of my mercs. I could have reloaded a save but it was too painful going thru some of those fights again and just figured I would hire a new 1, but some of the ones I was interested in are replaced or missing. (BTW did a night ops attack on this and with me using night vision over rebels who didnt have any they damn well could shoot pretty well in the dark)

Do they change based on my rep? Or is there some certain times when 1 shows up vs another?