It's very possible that Kodera made a mistake. He definitely is more analytical than most, but he's still a relatively young A-ranker with no captain experience.
However, there are potential good explanations for his choice too. By a certain logic, his team makeup makes perfect sense. Consider a few things:
Miura and Kumagai are both attackers. Both are used to playing defensively to shield an ace. On paper, their capabilities are similar. However, their /experience/ is very different.
Kumagai is used to being a shield who defends a less mobile shooter ace reliant on highly precise mass firepower at a distance. Kodera squad has zero shooters or gunners. Kumagai also has no experience cooperating with attackers or even all-rounders, as everyone else in her squad operates mid-range or long range. Kodera squad has three attackers.
By comparison, Miura is used to moving fast to support a highly mobile ace who uses handguns and scorpion. Kitori and Katori's styles are different, but his experience fits supporting Kitora much more than Kumagai's. Miura's experience also gels better with Okudera, since both of them are used to operating in unison as a supporting close-range pair.
By this logic, looking at their experience, Miura makes a lot more sense than Kumagai.
On the subject of triggers, Nasu with Meteora probably uses up a bit more Trion. Kumagai has Chameleon, which is also Trion-intensive trigger, but for two people with middling Trion levels, brief usages of Chameleon can get a kill more reliably than brief uses of Meteora. It's a more useful option to have on the table, I think. In fact, even the threat of Chameleon will change the tactics of others.
That's the rationale you could use to justify it.
I do think this line-up has big weaknesses. I think Kodera squad might suffer a lot for lack of midrange firepower, putting a huge burden on Kodera himself for supporting fire to cover three people. I think neither Miura nor Okudera have any ranged trigger, and I think Kitora's handgun isn't going to be a good lynchpin in a midrange fight, as she has middling Trion.
However, that might be meaningless. Remember one thing: we currently have no clue what triggers anybody has.
It's very possible that command gave each person some very interesting triggers, designed to see how they acclimate to new combat possibilities. They might be trying to draw out new potential in these fighters. We could see Miura running two scorpions to get him to be more aggressive. We could see Kumagai with mostly shooter triggers, to see her true skills as a shooter. Who knows?