Managed to find an alternative to altering all the registering and
spawning things for chickens. And no, it is not ASM: It seems that the
EntityJoinWorldEvent seems to be really helpful for us: whenever an
entity enters the world, we simply check whether it's a chicken, and if
so, we replace it with our pluckable chicken. At first glance this seems
like an easy way to solve the issue whilst maintaining high
compatibility with other mods, and on the efficiency side of things it
doesn't seem too bad. Now to finish up the whole pluckable chicken
module so that we can move on to new horizons!