And well, here's the mod I've been waiting to make, indeed.
This time this was easier to make with some experience in Audacity, beating my record from 1 day of just thinking of doing it to 10 minutes of searching and 30 minutes of making. Amazing.
Drop the file into the mod_overrides folder, then you should be able to find the track at the bottom of the tracks list in the heist setup menu.
If there's any issues with the mod, let me know. I'm open to SO:TL OST requests. Cheers
Loud track: https://www.youtube.com/watch?v=K7k6J1fDPOw (technically, the song is named "Hell Suite" but it's mostly known after that one moment that happens near the end of the game, where it's called "Welcome to Hell". Hint: WILLY PETE!)
Update 1: Introduced a new variant of the stealth track, making it more fitting to the loud track. File's currently awaiting approval as of 25/03 7:40pm.