Mika makes such a jolly leader in Orga's absence. Is he the de facto second in command, even if Eugene is the official one? I have no idea. Mika doesn't really give a shit about much of anything, and thus he grabs the gun as the quick way out. However, if somebody wants to claim the problem for themselves instead, Mika doesn't bother to argue. More scenes with McGillis and Mika might be funny, with McGillis being aristocratic and civilised even if highly pragmatic and Mika being... Well, Mika. There's always a huge tension in the atmosphere when Orga is in McGillis's company, but Mika naturally doesn't care. He just keeps popping those dried fruits or whatever they are.
Do they need to betray him? Maybe we haven't seen Turbine enough to really judge his personality, but I wouldn't consider it impossible he might give Lafter's hand to Akihiro if they confronted him openly and honestly. I was under an impression he had picked up these girls and offered them a home when they had no other place to go, or at least any better place. He must like all of them, but if one from the edges wanted to form a family with some other man he knows, maybe he would let her go. Considering how much Lafter has been with Tekkadan and away from Turbine's crew, she probably isn't his number one waifu.