I had something similar to this in my Dystopia City map for Interstate mod. I added bots to Conquest mode and forced them to spawn in "defense turrets" that would fire on enemies trying to enter the city. It worked pretty well for what I intended. The weapons the turrets used are weak enough to allow enemies to get through though as it wasn't intended to be perfect to the point of blocking access completely. They're just there to present a challenge for the opposing team trying to invade the city.
The spawn points limited it to bots only and all other spawns would not allow bots anywhere else besides those special spawn points. I placed the exit point of the PCO below the ground to prevent them from exiting the turrets. However as far as I can tell, this only works on stationary PCOs. If you allow the PCO to move, the bots inevitably find a way out, so you can't really do this with AA/Vulcans attached to vehicles that move around.
In your case if it's base raping you want to protect against then this method could be effective. Give the bots an unkillable PCO with a powerful weapon that fires really fast projectiles (so they don't have to spend as much time setting the trajectory to the target) and they'll do a good job keeping out the badguys provided the AI coding is good and there isn't problems with the ai templates. Just be sure to limit their range else they may kill things further out then intended.
And yes, even though the bots won't ever leave the PCOs, you still need valid pathmaps and stuff. But if you never expect to have them do anything but man the stationary PCOs in conquest mode, you can get away with default all black pathmaps and a basic setup. So long as there isn't idle conflicts with control points or anything, the bots won't be distracted and will be quick to respond to enemy threats. It's not normal for a bot to be confined to a PCO so they almost take on a personality.
Just go up to one of my defense turrets in Dystopia City. Choose the team that spawns in the city. Go to a turret and fire at it. The bot will even "look" at you when you do this as if to ask why you are firing at them.
Something you probably wouldn't notice at all under normal circumstances.
There's a whole can of worms you have to go through to add bots in Conquest mode. Good luck with that.
Look at my Dystopia City map on how it's done. While the process is combersom, there are some benefits to adding bots in Conquest mode. You get full control over ai templates. Normally you can't replace existing ai templates for a vehicle/PCO in a map side mod without modifying the template in the mod files itself. (interstate has a lot of duplicate/bad aitemplates so it crashes if you try to setup proper singleplayer mode). But in Conquest mode, you have to manually load in all the aiTemplates you need so you can define aitemplates yourself and not use whatever the mod uses. Thus you can make the aitemplates all map specific.
The downside is you need to make sure to load in aiTemplates for every vehicle you expect them to shoot at and it's especially important you get ai templates for soldiers, kits and handweapons loaded else it will crash. But once you get over that hurdle, there's some interesting things you can do. Like have bots act as a anti baseraping measure. Now that I think about it, no mod/map I've seen had done it this way. It's always been the old deathbubble stuff. Adding AI to a map is completely server side to, so you don't have to have the client do anything special like download the map. You can add bots to maps that never even had a proper singleplayer mode too. The server controls what the bots do and only the server needs the aitemplates/pathfinding stuff. So it could be a superior solution to death bubbles.
It would certainly be a more elegant solution. If the the AI is made to be just a little sluggish in responding, it would give enemies a chance to leave if they entered the base's airspace by accident. But if they stay to long, the bots will take them out quickly. Anti soldier turrets could also be created and placed around the area to protect against baseraping on foot/land vehicle. Though note that creating new PCOs isn't possible as a server side mod. If you are creating a new map or modifying a new map and expect clients to download that map to play it, then you'll have more flexibility in that regard. Else you'll have to reuse existing stationary PCOs to do the job. You may get away with having them fire different projectiles though. I forget the exact rules on server side modding in terms of what can be done and what can't so I'm not the best person to ask about that.