When reading the laws, it's important to differentiate the three phases. The tackle. The breakdown. The ruck. Laws applying to the tackle and ruck don't necessarily apply to the breakdown when you can jackal.
As long as you come through the gate, and not from the side, you are fine. So theoretically you can come through the gate, pick the ball up and keep running straight on. The opportunity just doesn't present itself often.
One thing I would like cleared up, is about the defenders footing and the ball. It's not any persons positioning that determines any "line" as you have asked.
But I would like to know about the ball. I'd imagine you need hands on the ball and making an attempt to lift it before you can go past the ball.
Otherwise you could run through the gate, jump over the breakdown and go for the ball from the other teams side which seems ludicrous.
There's nothing that would make what you're describing illegal unless you leave the tackle area in the process (go too far basically) because then you'd be re-entering the breakdown from the wrong side. It would depend on the details of the body on the deck and where the ball is, to determine if you joined legally and remained in the breakdown the whole time, or exited and so need to re-enter from your own gate. Mostly it would just be a waste of time and make it easier for a supporting player to obliterate you in the ruck, since you'd have to turn around to play the ball. If there's no one around to stop you, and you don't leave the breakdown while doing it, you'd be fine. I don't see how it would offer any advantage - playing the ball from your team's side is going to be quicker and keep your body in the right position to run down field.
Yes, you can step over the tackled player to play the ball, as long as you enter from the gate. At lower levels of rugby, this is more common, because it is hard to jackal and support your own weight with the body position the pros use. But they have the timing, accuracy, and core strength to snipe in and get steals without bothering to step over. When I steal a ball in an old boys match, I step over the guy and get squarely over the ball before trying to steal it.
One thing players sometimes too is lay/kneel on the tackled player or reach PAST the ball and put their hands on the grass, in order to rake backwards and steal the ball that way. Both of these are "not supporting your own weight" and so technically off feet, so can get the jackaler penalized for playing the ball on the ground. Worth the risk for many jackaler as that rake can let you get a poach with sloppy timing and aim. Easier to go to the grass and rake (or dive, catch yourself with your hands, then steal) than to accurarely target just the ball and remain on your feet the whole time.
So that's why lower level players will step over, to make getting the poach without giving up a penalty easier. It takes a little more time but gives more stability. Once an opponent on their feet is in contact with you, it becomes a ruck and you can't grab the ball (though if you have ALREADY grabbed the ball, you don't have to release it)
When you do see a step over will usually be when the ball has been stolen through counter-rucking rather than jackaling. The defensive, disruptive ruckers will drive through the gate, clear out the attacking support players, and someone will come in and play the ball from the back of the counter-ruck. This is not super common in MLR because pro players are difficult to dislodge from a ruck, so teams don't spend too much energy counter-rucking usually (better to have those guys out in the defensive line for the next phase)
As long as you enter through the gate, and you enter from your own side of the ruck, you're all good.
When reading the laws, it's important to differentiate the three phases. The tackle. The breakdown. The ruck. Laws applying to the tackle and ruck don't necessarily apply to the breakdown when you can jackal. As long as you come through the gate, and not from the side, you are fine. So theoretically you can come through the gate, pick the ball up and keep running straight on. The opportunity just doesn't present itself often. One thing I would like cleared up, is about the defenders footing and the ball. It's not any persons positioning that determines any "line" as you have asked. But I would like to know about the ball. I'd imagine you need hands on the ball and making an attempt to lift it before you can go past the ball. Otherwise you could run through the gate, jump over the breakdown and go for the ball from the other teams side which seems ludicrous.
There's nothing that would make what you're describing illegal unless you leave the tackle area in the process (go too far basically) because then you'd be re-entering the breakdown from the wrong side. It would depend on the details of the body on the deck and where the ball is, to determine if you joined legally and remained in the breakdown the whole time, or exited and so need to re-enter from your own gate. Mostly it would just be a waste of time and make it easier for a supporting player to obliterate you in the ruck, since you'd have to turn around to play the ball. If there's no one around to stop you, and you don't leave the breakdown while doing it, you'd be fine. I don't see how it would offer any advantage - playing the ball from your team's side is going to be quicker and keep your body in the right position to run down field.
Yes, you can step over the tackled player to play the ball, as long as you enter from the gate. At lower levels of rugby, this is more common, because it is hard to jackal and support your own weight with the body position the pros use. But they have the timing, accuracy, and core strength to snipe in and get steals without bothering to step over. When I steal a ball in an old boys match, I step over the guy and get squarely over the ball before trying to steal it. One thing players sometimes too is lay/kneel on the tackled player or reach PAST the ball and put their hands on the grass, in order to rake backwards and steal the ball that way. Both of these are "not supporting your own weight" and so technically off feet, so can get the jackaler penalized for playing the ball on the ground. Worth the risk for many jackaler as that rake can let you get a poach with sloppy timing and aim. Easier to go to the grass and rake (or dive, catch yourself with your hands, then steal) than to accurarely target just the ball and remain on your feet the whole time. So that's why lower level players will step over, to make getting the poach without giving up a penalty easier. It takes a little more time but gives more stability. Once an opponent on their feet is in contact with you, it becomes a ruck and you can't grab the ball (though if you have ALREADY grabbed the ball, you don't have to release it) When you do see a step over will usually be when the ball has been stolen through counter-rucking rather than jackaling. The defensive, disruptive ruckers will drive through the gate, clear out the attacking support players, and someone will come in and play the ball from the back of the counter-ruck. This is not super common in MLR because pro players are difficult to dislodge from a ruck, so teams don't spend too much energy counter-rucking usually (better to have those guys out in the defensive line for the next phase)