So the idea i know might not be doable but you could put in place on party finder a registration system. the Manager or venue owner could register the venue (so would be registering the full name, short version name (example PNX) as well as where it is located and days/time its open. then register up to a max of 3 players who will be advertising for them.
Now the reason i even make this suggestion is the sheer number of venue ads some can have. like on aether ive seen upwards of 9 from one place one night. I know the community somewhat has a tentative 3 max rule amongst most of them but some don't adhere to this and think its ok to spam and drown out other venue ads or people not posting venue related stuff.
So this system would ensure that only the regsitered 3 players could have ads up for said venue on the nights they are scheduled to be open. so you could have the system programmed to allow it a few hours before. Now, could this be bypassed. People would certainly find a way but thats why you get them to register the full name, any short form name as well as world/housing disctrict/ward/plot location. Other then when people have a beach party this would be easy to program in for the system to recognize that more people are trying to put up ads and wouldnt allow them too. thereby keeping the 3 players designated as the only ones able too.
alternatly just add a RP tab to the party finder so people can spam that lol