Every NPC eternally standing in the same position is just plain boring. If NPCs could walk - or even run - there'd be many new ways to use them!
The way I'm thinking of it working is something similar to the Custom Paths for platforms/blocks, but it's connected to the triggers somehow: you add nodes/points where the NPC will be able to stand at. There could also be something similar to the "idle time," except triggers can be used to determine at which point(s) the NPC will stop at to stand, if enabled (I'm not sure what types of triggers would be added, but I think something could work - maybe something like the "Sleep until..." function?). Btw, maybe there could be different kinds of nodes to add, like "run" nodes, "walk" nodes, "activate trigger" nodes, "rotate this" nodes, etc. If the nodes were used effectively - if ever considered by the dev team, we could make NPCs much more interesting and lively!
All that may or may not have made sense, but I tried...