OK Thanks for the info SM4 Pirate.
When it comes to offsets, yes they are only a defense against opposite direction traffic. Basic rules of the air (CAR's) say to veer to the right when passing opposite direction traffic so there shouldn't be a conflict there between left and right offsets. To mitigate this risk that someone does choose to offset to the left, I would be offsetting by some random amount say 1.7 nm or whatever.
Here is some of the relevant CAR...
162 Rules for prevention of collision
(1) When 2 aircraft are on converging headings at approximately the same
height, the aircraft that has the other on its right shall give way, except
that:
(a) power-driven heavier-than-air aircraft shall give way to airships,
gliders and balloons;
(b) airships shall give way to gliders and balloons;
(c) gliders shall give way to balloons; and
(d) power-driven aircraft shall give way to aircraft that are seen to be
towing other aircraft or objects.
(2) When two aircraft are approaching head-on or approximately so and
there is danger of collision, each shall alter its heading to the right.
I suppose all you can do is try your best to reduce the chances of conflict. You can never eliminate them.