All I can think of, if it was me who tried that with the kitties, I'd end up with three kitties who'd completely forget that raw meat is for eating. They'd lap up the delicious gravy and then get to the cold, raw meat and shun it. Maybe Molly would eat the meat, because she loves to eat and she'll eat and eat and eat until I take food away from her. But Willow and Buffy, they're more spooky. I would be too afraid to change their meals for fear they'd stop eating their raw meat.
But if you added just a few drops of gravy, just to add a little flavour/smell to entice the kitty to eat, that could work. I've done that with Buffy back when I was trying to get her to eat raw, only I used small amounts of canned food instead of gravy.