the insulator is used as an acoustic treatment for underhood noise dampening, its unlikely it was designed to protect the paint. It costs manufacturers hundreds of thousands of dollars to D&D parts like this, protecting under hood paint could not be a justification for the substantial costs. i dont work for them but i dont believe toyota would do that
It's fibreglass because its cheaper to manufacture, it saves money on the production line because another process dont have to be added such as to trim the edges, plus its lightweight and performs well acoustically. but its is liable to sagging, you may find many retainers to prevent it from doin too much of this. but if you want to just take it out, nothing will happen except a bit more noise. my car didnt even come with one. better to ask toyota what fabric they recommend, as i assume materials used will need to pass heat and sagging requirements. good luck
