I don't think I've seen a full "system" for it. But most escapes focus on getting your head and shoulders to the floor and sort of shoulder-walking away. If you can get a 2-on-1 grip on one of their arms and pass it to one side of your head you can escape yourself into their closed guard, top half, or sometimes even brabo choke them as you escape. The closest thing I've seen to a system is making sure to always force them on the side where their body triangle is locked against the floor while getting at least one C-grip facing down on their top arm. That kills some of their ability to adjust the body triangle and it helps pin their hips to that side so that when you start getting your head and shoulders to the floor, they can't adjust or bring you to the other side as easily. The C-grip facing down on the top arm is better at stopping the choke than reaching up from underneath with 1 or even 2 "chin-up" grips.
I think part of the reason we haven't seen a very detailed back escape system is that there are many different styles and hot takes on back control. So there's not a unified way of controlling the back although we're closer to that point now than ever before. So until recently there's been a lot more variety in whether people use hooks, ankles crossed behind the hip, or body triangles, as well as whether they fall to the top-arm or bottom-arm side.
The most common back control at this point is body triangle with the lock facing upwards while falling to the under-arm side. That's probably the best starting point to start to think about a back escape system.
