As it says in the topic, would it be possible to make what Filch Lizards sometimes spawn with configurable?

I think this could be a nice feature to play around with - especially in large modpacks.

It is actually possible to customize the Filch Lizard item spawns with a loot table editor, you can find the filch_lizard folder inside the entity loot tables folder. A config option can also be looked into if there's demand for it. :)

filch_lizard_spawn controls what items the lizards spawn with. You can control the chance for a lizard to spawn with an item in the config (25% chance by default).
filch_lizard_steal controls what items the lizards are interested in stealing.
filch_lizard controls drops for when a lizard is killed (currently empty for now).

You can find an example of adding custom loot to it with LootTweaker in Hexxit II's \scripts\loot\hexxit_loot_changes.zs L#35.