Mine was a LOT worse than that, and managed to fabricate a panel -to be honest, yours looks like you should be able to remove it, de-rust it, paint and re-fit.... honestly it does NOT look bad!
Mine took 2 days of fabrication to fix, one layer of the bottom metal was basically missing, and 90% of the front curved bit beneath the vents.....
Needless to say it is now anti-rust primered, and lots of top coats to protect, oh, and waxoyl in the cavity behind the curved bit below the vents....
Hope that helps a bit, I unfortunately don'y have any pics of it off the vehicle