Hmm... after reading this chapter I got a sudden idea (an old one actually):
Arika "Queen of Calamity" x Nagi "The Hero" = Negi
with the same type of couple, we could set:
Eva "Queen of Darkness" x Negi "The Hero's Son" = ??? (Just kidding, but it'd be fun to watch).
Sure, I agree with most of your hypothesis and there's something disturbing me...
1. After Nagi acquired the title of Hero, then Ala Alba split up:
-Nagi taking Arika (perhaps)
-Gatou and young Takahata taking Asuna (This is showed before in Asuna's dream)
-Albireo and Eishun going back to the old world, they might be taking the baby Negi to Britain then hide themselves in Japan (Mahora), or they just going straight to Japan?
-Rakan stayed in the new world and hide his existence (This shows how the people on the new world are surprised when he showed up).
2. Now my question is, what happened after the war is over? There's a sudden change to Ala Alba's condition and where exactly Nagi meets Eva? Is it before the war? Far after the war? Since I don't see Asuna on the flashback where Eva is involved...
"Hard work will get you close to the goal, a good attitude will get you right to the goal, but the love of God will get you beyond the goal"