Why should the game freeze for looping?

I just want to add transform red mushroom cow to brown (from "Brown Mooshrooms" mod), and back.
OR
Make transform cow to brown/red cow with chance 50/50

I got game freezes when Mob1 -> Mob2 -> Mob1 because each mob was firing the change code in the same tick they were created in so it was infinitely looping within a single tick. It could be handled by preventing the registration of recipes which result in something that is a valid input.

The bigger design issue is not losing the current villager profession changes.

The biggest hold-up preventing this is I haven't figured out a good way to prevent looping (i.e. game freezing) or how to handle the villager professions (e.g. Illigers). Or the special handling that slimes -> magma slimes require.