Custom behaviour on paths may require an unrealscript callback, gotta meditate over that.
Yes and no depending on combat situation, a closer creature is Hunting - ignoring paths and charging at Player directly, if creature is far away and player is retreating out of sight such a reachflag for a low brained monster will cause a path lock. Condition is if creature cannot open doors (just a bool and nothing with Player doors - they are not very logically connected) won't pass this flag. Majority of doors are BT_PlayerBump and then... flag won't stop a Skaarj to try forcing door unsuccessful but... not all souls are bunching in spot. Of course this is not a real Map situation (not yet...) but I think it worth adding options for future, maybe some people will have a clue what to do and "how to" for guiding Pawns how they want, spreading troopers, smarts on the right, stupids on the left - even switching sides based on... daylight, lol. R_DOOR reachFlag can be used as a timer hint - a pointer - switching happens here between 1:00am 10:00am, changing path property in run-time, not a complete lock but Player Lock or Monster Lock not for everyone like a BlockedPath - of course options here are... countless.
So far I cannot expect a team-work here with some mappers but... maybe in time a bad-ass mapping team will show up and options are good if are ready to use.