Been doing more thinking on this . I may be off base here, but it sounds like there are two generally accepted way for a spell to target a thing: Perceiving it as the magus, or perceiving it with intellego (extension, as the magus). Perhaps it could be the other way around? The spell to target in hermetic magic, the spell must be able to perceive the target (with intellego) or the spell needs to perceive the target with the magus as its proxy for intellego.
Hmm. After this discussion (which I enjoy) I went back and read through the Lesser Limits of Hermetic Magic again; The limit of Arcane Connections states that you cannot affect an unsensed target without an Arcane Connection. Intellego gets around this somewhat. It also, coincidentally states that you cannot Perdo Corpus people on the other side of a wall unless you first perceive their existence. The above accepted Perdo Vim target Room for infernals is, assumed, getting around that by targeting the room. Basically, you can't kill Schroedinger's Cat with Perdo Animal, because you aren't sure if its there, and you might use the kill-living spell when you needed the destroy-corpse spell.
But ... We're now talking about Creo magic. Creo magic isn't targetting the 'effective' target. Just like casting Pilum of Fire, the target is the fire, the man getting burned a fortunate side-effect. If you cast Creo imaginem to paint your own Intangible Tunnel (which you perceive as the magus) then it creates a visible species in its location. by the strictest reading of the Limit of AC, this is fine. If you cast CrIm to paint someone else's tunnel, that you can't perceive, then you'll probably fail. Generally agreed? (I'll assume you agree with me, because you aren't going to respond before I actually finish this post, and it makes a better narrative.)
But what about the room spells? Room CrIg still fills a room with fire. Room PeVi still nukes all the demons in a room. Would a room-target CrIm be able to paint all the intangible tunnels in a room? I'm currently leaning towards no, actually. In fact, I think if you had second sight, could see all the Intangible tunnels yourself, you still couldn't paint them visible with a room-target CrIm - because I think you need a group target. Those intangible tunnels you're making visible are each a separate item. This second point is more of an opinion in my mind, and I don't think saying the room-sized spell is doomed to fail in all games. I might even allow it with added complexity levels to have the different parts. I digress.
Back on track: This is instead my thoughts on creo magic. You cannot tell magic to do something you don't understand. An apprentice, raised in seclusion by a Criamon, taught great levels of creo magic, animal magic, and provided with books and tutors, if told by his master to use Creo Animal to conjure a platypus, will fail.
"As a skilled practitioner of Creo and Animal, I can conjure anything, master! Tell me, what is a platypus that I may conjure it?"
"It is an animal. You may begin conjuring now."
Thus ends my philosophical argument of Criamon's Platypus.
Translating this to our current discussion, let's assume instead of intangible tunnels, we're playing with demons again. A room-wide Perdo Vim can damage all the demons in a room. Can a room-wide Creo Imaginem paint all the demons mauve? Dear magic, please make all the demons in this room illuminate with hideous color, thanks magic. Like a computer, magic isn't thinking for itself, its carrying out its instructions. You say paint the demons, it pulls out a list of demons in the room from your head, finds none, 404.