I just thought about this idea,and instead of getting rid of forts,let's add this idea.
Instead of having the whole base fort killer,why not have certain spots where you must stand for kills to count.
Red circles can be found in bases when fort killer is active. There will be 3 big circles in the first room. To gain points for your gang,you must get your kills while standing inside the red circles. If they are all full,you must kill players standing in it to get in the spot. Each circle can hold about 6-7 people.

Now for the second/third rooms(if there are). They only have 2 circles,but these hold 8-9 people.
And for the flag room,you can score big points for your team. Stand in the red circle in the flag room can multiply your kills by two while in it. The flag room circle holds 1-2 people.
I had this idea to seperate fort killers and not have them spam the entrances/exits and so people can have a "chance" to base. What's the point of trying to take a base if you and your gang can't make it past the first room to try to move on to the flag.
I think this is a unique idea for people who would want to base and not get caught up with the fort killer so much.