Stole some wrestling, improved it with BJJ
Lately I've been impressed by wrestlers adapting to BJJ and bringing their grips to the game. This last Friday I was on the receiving end of six years of wrestling, and afterwards I learned what he did and quickly stole it and worked my BJJ into it. The technique he showed was a turtle turnover to pin that can turn into a shoulder lock, and I added a triangle finish. I can see a lot of potential with this.
Let's say they are turtled and you're on their right (so they are to your left). Rather than taking the harness, you get a 2-on-1 on the near arm (their right forearm), with your left arm reaching all the way around and under their torso to do this.
Now rather than wedging your left knee under them and posting out on your right leg (like Luis shows in SoFlo, or the first step of the reverse omoplata on TampaBJJ.com), you post your left leg out behind them and put your right knee near their armpit, driving your hips into them.
You might feel like they can return to guard with your legs like this, but the 2-on-1 prevents them from turning towards you, especially when you start applying the pressure in the following steps.
Start breaking them down with the 2-on-1, pulling their arm back as you circling towards their head, sprawling to drive them down on their right side (so they are turned away from you). As soon as you can, release your left hand and bring it around their body, then reach under them to get an underhand grip on their forearm. You've now got their arm twisted back and you're holding it like a baseball bat.
Keep pulling their arm behind their back and circle towards their head. They will have to turn away from you (to the left) and go to their back to relieve the pressure on their shoulder. As soon as they do, make chest to chest contact and take your right hand out and reach behind their head. You now have side control with their right arm held behind their back with your left hand.
You can keep circling towards their head to wind their arm up into an eventual shoulder lock, but I'm lacking details of how to finish this cleanly (so they don't just keep trying to turn into you).
The wrestler I was working with called this "ball and chain", but others have said that's usually when you pull their arm between their legs, so I'm not sure of the wrestling name.
Where I added my own jits was by seeing that I could easily just mount into a triangle, since one of his arm is out of the game. Just step over and get a high mount and you've got it.
I'm still working on it, but this really excited me, since I can also see the initial 2-on-1 being used as a great reverse omoplata setup, by pulling the arm back so I can slip my leg into the trigger position for the roll.