I would love to see some more options for path finding. What immediately comes up in my mind:
(a) doors
(b) fields

(a) should control whether a path may traverse closed doors. There are monsters that can open doors, so a closed doors should not be a problem for them

(b) should control whether a path may traverse fileds, such as fire fields or poison fields. This can be used to differentiate paths for monsters that are immune to e.g. fire fields from monsters that are affected by e.g. fire fields

Pathfinding does have a flag to ignore doors. FP_IGNORE_DOORS

As for fields, that'd be a much harder implementation since you can walk through them already.