I took a long, hard look at the main movements I use while grappling and began compiling a list of "<this> exercise aides <that> move"
As an example, break down your arm-drag. It's, at the bare bones level, just a 1 arm row. When you arm drag though, you're generally pulling across your own body at an angle (from the far side to the near side), so we just need to alter our 1 arm rows to pull across and simulate a real arm drag instead of the traditional single arm row. These are great if you have access to TRX straps. (or a rope tied to an anchor point works well enough).
Squeeze drills are another one I think are much more important than bench/squat/dead lifts/etc. when it comes to functional strength for grappling.
I remembering hearing an interview with Frank Mir a while ago where he talked about how he could hold his guillotine for a full round at 100% power without gassing.... I didn't believe it, but thought it would be a great basis for a grappling circuit.
Fold a kicking pad in half (or slightly deflate a basketball) and wrap up a guillotine on one side... with a constant squeeze, clamp down as tight as you can for 60 seconds. Then, rest 10 seconds & switch to the other side. Squeeze the shit out of it for 60 more seconds, rest, and then move on to the next exercise.
I do this for guillotine, triangle, arm-triangle (palm to palm & hand to bicep), & my guard squeeze. And then, I take a tennis ball and pinch it between my neck and one shoulder like I'm defending a rear naked choke. I'll hit the ground & roll around for 60 seconds, making sure not to let the ball slip. Then, once the time is up, I'll swap & do the other side.
CIRCUIT:
Guillotine @ 60sec each side - standing, go to your back, roll over on top, etc. (move around, but squeeeeeze)
Triangle @ 60sec each side - on your back, roll to the top, etc.
Arm triangle @ 60sec each side - on your stomach, stay flat & low. Switch up your grips a couple times through the round.
Guard squeeze @ 60sec 2x - keep your guard tight, roll around, one hip to the other, etc.
Tennis ball @ 60sec each side - pinch the ball between shoulder & neck, move around, forward/backward rolls, etc. (just don't let the ball slip)
I'll usually go 2 or 3 times though in this order (that way I'm alternating between arms & legs).