Mob Figurines, A Beacon Modifier

Mob Figurines would be tiny statuettes depicting various mobs, appearing to be carved from whichever material Mojang deems most appropriate.

They would be found in loot chests and occasionally sold by the Wandering Trader.

While mostly serving as ordinary decor, decorating the pyramid base of a Beacon with these figurines would extend the Beacon's effects to the placed figurines' corresponding mobs.

The most obvious benefits are protections to Villagers, Wolves, Horses, and other friendly mobs, but one could also enhance hostile mobs if they wish. Since Regeneration doesn't harm Undead mobs like Healing does, this doesn't directly lend itself to designs for large-scale mob grinders.

Placing a Mob Figurine on top of the Beacon block itself could limit the Beacon's effects to the designated Mob, should the Player decide on an improvised challenge.