The thinness of the material is not important as long as it is rigid.
The area of the diffuser vs the room volume is an issue. If you can 3D print panels at sizes over 1m then it’s a good option. I have no idea about the process though, hence can’t comment further.
According to a seller on Etsy who sells a pair of panels, covering an area of 108cm x 61cm and 15cm deep weighs 27kg. Do you think that is very heavy?