I don’t know if it exists already but I’m sure someone else has thought of it already. When you hit a Mob with a Sword (or Bow) with Fire Aspect (I or II) (Flame I for Bow), they should be a light source. Let me know what y’all think eh.
It would make sense that they would light anything light-able and create a light source which would be really nice to see and utilize when caving either without Torches or just a cool affect in general.
Make a mob immortal with cheat codes, place and light nether rack, then shove them in the cage. (It would work if flaming mobs were a light source. Oh well.)