I agree that it's high time we got some Danica content. Being under Klaus payroll could allow her to infiltrate Langdon's organization and help out a bit. Langdon shouldn't know what happened to her.
Also yes, MC needs training partners because he has outpaced all his friends. Deryl may manage to put some fight if he finds a good combat expression for his power, but it's foreshadowed that Deryl and MC will try to improve themselves through researching monster bodies, so I don't expect much sparring other than testing their creations.
Truth is that the game doesn't show many level 3 HERO agents. Most of them are weaklings. The two that we knew about, Troy and Gillibrand, are either dead or out of commission. So I expect MC to start training with the Lieutenants. There are bound to be a couple more levels 3 according to Lisa, and it's possible that MC can do well against the level 4s. Jill's performance was pitiful, so she seems like a good stepping stone. (Edit: Apparently some HERO agent claims to have seen a dozen level 3s fight, and half of them took part in Diamond Battle)
I've thought about the "new system". It's unlikely that teams will break up, since the captains are way older than the new generation of level 5s and there is a huge difference in power. Perhaps we may see Henri and Benrhardt creating their own teams since Cthulu is the only team with 2 captains. I think the system will introduce a way for the teams to incorporate 1st and 2nd class agents into their ranks, or at least in their sphere of influence, something like Hogwards Schools. The higher ups will be mentors/handlers to lower class agents.
Unless Ella comes back quickly, I expect some time leaps, and perhaps even MC formally joining Team Reaper.