Its possible, I think it uses the spawn rate of movs per tick and the ticks can be increased. Or you can download a plugin for it, I was reasearching, I found one but its outdated and its version is 1.10. There is another method which might work is my increasing the mob spawn distance to how many chunks around the player. I think default is set as 8-10 chunks, idk if you edited it in the past but I think the cons of this would be more entity lag. Maybe try increasing the spawn distance around the player, and test it. I wouldnt suggest playing around to despawn certain mobs such as villagers or other mobs. Some players like me or me only idk, have plots/houses with villagers in them, no clue how it got in there but i bought the house that way and its really helpful to me.