Reset actor material to original material

I’m making a game where your character can have his back to a wall. I currently set that wall to hidden. Then when the camera no longer hits that wall, it becomes unhidden.

This works for multiple walls and objects being hidden at once, putting them into an array and then pulling 'em out as necessary

However, the character has his back to a hillside, it will hide the entire landscape.

I want to change the material of the landscape / wall / etc to a see through material, so that you can still see that it exists while it’s being seen through. Is there a way to put default object materials back on the objects?

Would it be better to mask individual materials instead of hiding them? Would using masks on every material cost significant performance? How would I change the mask value of the correct object’s material?

I’m using blueprints. I’ve currently set this up to work on the character, so it’s easy to reference the character and his camera.

Not an amwer, but they reently did a twitch stream on how to hide/change objects btw the player and camera.