Prevent anyone besides party leader from initially entering zone transition doors

[uuRETCH]

Unsure of how feasible this would be, but I feel it would prevent a lot of accidents if party members were altogether denied from using any zone transition door that was not used by the party leader.

Zone doors used by the party leader could be highlighted once used, in similar fashion to the 'Reveal Players' function. Signals to party members where to go if they've somehow gotten too far separated in the area.

[miredirex]

Not a bad idea, but perhaps too restrictive. In my opinion, best course of action is to first resolve the bugs surrounding NPC ownership transfer so that cell changes become less fragile and desync-prone

Relevant cosi comment (this has been discussed in #questions a while ago):