Inside space at the scrum

Players now have to be 5 metres back from the hindmost feet of the scrum. This has two main consequences. First, space is created on the inside of the fly half (10). Second, your back row moves need adjustment.

1. Inside space

The extra space from the back of scrums means there is more time for backs moves. It is likely that most defences will "drift" from scrums to cover the opportunities to move the ball wide.
The drift will leave a potential dogleg in defence. The defending openside flanker is at least 7 metres in front of his 10. As a coach you have to think both how to defend this dogleg and, offensively, how to exploit this gap.

Defence from the scrum

First decide how to plug the defensive gap inside the 10.

• You could use an "up" and then drift defence, where the openside flanker does not close down the space so quickly, but allows the back line to catch up with him. So the back line moves up 5 metres and then drifts out.

• Your scrum half (9) could cover the openside. From a scrum on the right side of the field, he would go round the other side and keep close to the back foot.
  
  On the left side, he could pressurise the attacking 9 with a view to running out into the midfield.

• Your openside flanker runs across and then out, to cover the opposition 10, and your number 8 fills the gap inside. Your openside lock forward should be aware that he needs to get up from the scrum and then hold his ground.

All these defences are relatively passive, allowing the attack some time and space.
As with any defensive system, the back line should vary the types of defence it runs to keep the attacking team guessing. A couple of passive alignments should be followed by an aggressive system.
Perhaps the team can risk leaving the inside channel less well defended, with the number 8 aware that he might have to cover to cut down the possibility of a wide move.

Attack from the scrum

The defensive problems highlight the attacking opportunities. The "inside seam" of space next to the defending 10 can be exploited with blindside winger moves or switch plays.
Mix these with wide moves and the defence is likely to be stretched trying to cover all the possibilities.

2. Back row moves rethink

Most back row moves aim to attack the space to the sides of the scrum.
With more space outside the sides of the scrum, there is a strong case to aim a little wider than normal. With a stable scrum and perhaps a friendly wheel, your number 8 could aim wider with the pick and go.
However there is an equally strong case for your number 8 to pick and pass to your 9, so he can attack the 5 metre gap between the back of the scrum and their 10, with the flanker in close support.
Another area to explore is the back row breaking with the scrum half before feeding the backs. This will draw in the opposition 10, creating spaces further out.