You have the right idea! They are just forcing a modulation throughout the song, for an otherworldly / uplifting effect.
The only part that I'd not necessarily agree with in your analysis was the Verse, which I'd say is in B Major, I - IV - vi - V.
There are also tons of suspensions happening because the bass / keyboard isn't always following the guitar strictly, and vice versa. I didn't figure out the specifics there, but this is a really simple pop song at the core -- decorated with lots of lush chords.
Rush do this "continual modulation" all the time in their compositions. You can actually hear a lot of this in Nirvana, too. Especially on the Nevermind album. Devin Townsend is also really big on it, too.
-Carl.
Carl King[br]GuitarTricks Video Director / Producer