So 5" is a lot. You could certainly build out over that if you felt so inclined. I'm assuming there's some way to maintain access to the fuse panel and still create some measure of sound barrier.
Don't know if it helps, but here's (link below) is what we did with your area (which admittedly is completely different from yours. Steel framework comprises a skeleton upon which wood panels are installed (via rivet nuts). Pretty much everything comes off with 4 bolts... 4 bolts to remove the battery box cover, 4 bolts to remove the inverter / electric area cover, 4 bolts to remove the upper dash, etc. So everything remains accessible.
Hit this link. Pretty much everything I'm talking about is on that page of our build thread (scroll up & down)...
Our dash build