Player to Player Collision

[Glenn the Great]

The only idea floated so far that I think is any good is the one where Player A pushes against Player B and then the two swap spaces.
This could create an interesting puzzle game out of moving idle players into inhospitable locations.
Something to think about with this idea: Should players be allowed to push each other out of the way during combat? If so, it could create an interesting team dynamic (off-tanking), and a PvP dynamic (fighting over access to a mob's loot drops).

It would be too much of an aesthetic sacrifice to impose a "no 1-tile-wide pathways" rule on the map design, and there'd still be the issue of two players teaming up to block a wider pathway.

I don't think the jump command is a good solution because there are going to be odd player/world placement situations (ie: idle player is in a T-intersection), where it would be ambiguous as to where the jumping character should land.

I'm not a big fan of the no-collisions ever idea because of the technical consequences of players stacking on top of each other.
It would mean a lot of things for gameplay: X-vs-1 combat with mobs, targeting, PvP.