The sheet metal would be cost-effective if done correctly. The thread below pretty much closes that area with an rsr oil cooler mod. While you have a little more open space, it should still be doable. Theres also a company that sells premade cuts for that mod for about $100~300 if I recall correctly.
https://forums.pelicanparts.com/porsche-911-technical-forum/1023156-front-oil-cooler-duct-mod.html