Will the scenes that have to be told through this characters perspective be protagonist (OS) scenes, or IC scenes? Remember, they’re two different things structurally. If these are OS scenes, I wouldn’t hold back. Say what you gotta say.
If they are IC scenes, keep in mind that the IC is the you perspective as seen by the I perspective. As long as you don’t show all of this characters cards, even if this character narrates or the audience gets a glimpse into this characters thoughts, I think it works. As long as the audience is metaphorically wondering “what are you up to?” I think it should still fall into the right perspective.
Think of all the scenes you see in a movie where a character gets an idea and then grabs their keys, or runs into a building, or otherwise starts putting some plan into motion, and then the scene cuts to something else so that the audience doesn’t see what this character is up to. That seems like a pretty easy way to have an IC scene from the IC’s pov but without the audience knowing everything.
(note:I speak as though I know what I’m talking about, but I am, of course, guessing about most of that)