[Feature Request] Allow configuring of spawn & despawn distance

Hello,
I've been running a modpack with Lithium installed, and I've noticed mobs outside the 128 block despawn radius tend not to despawn (I imagine because they're not being ticked). Since Servercore is in control of the mob caps, it would be really nice to also be able to adjust the mob spawn/despawn radius (in blocks). Not sure if this is feasible or not, but thought I'd suggest it anyway.