Im really diggin that idea! I've seen so many alternative routes in this game already, im sure its going to be littered with secrets
It sure seems that way. I've been rematching the video to see if there's anything neat in it. At 12:48 you come across this wall. Once you demon pull it quickly stretches away from you. I don't think you can jump to it or you'll miss out on a red and blue wall. While they might just be secret rooms that will challenge you or something and not really alternative routes I'll call them Alts anyway.
Along that route you'll see a bluewall. Alt1
Right after breaking a red wall, you come across one directly in front of it, he leaves it alone. Alt2
It may be the light playing tricks on me, but something that looks like Divinity statue can be spotted in 13:40 in the very corner of the room.
A divinity statue at 15:18. There seems to be lost souls in the ceiling! Right at the end of the hallway and the upside down, glass dome.
The stinger enemies are stronger in this; they emit a gold aura and they like to throw bombs at the fragile floor or wherever you're currently standing.
Harpies have a lance move and it seems a little tricky to avoid. It appears that you can actually cut their wings, too. I can see them becoming a nuisance with that long range move on the ground, not to mention that it looks tricky to parry off.
There is a nice combo with the shotgun at 16:56. It has massive pushback but not enough that it completely grounds the enemy like the arbiter does. Leaves a nice trail of smoke and it's obviously useless against the demonic shards due to it's slowness and short range.
At the end of the fight he says "How do I get back" and there seems to be two routes you can take.
That's it.