AI has improved over recent years so it would be interesting to
increase intelligence of NPCs.
1) reinforcement learning was used successfully already in 1990s
to create more intelligent players/monsters in roguelike environments.
I just listened podcast about facebook where they have managed to make
AI controlled player to advance to approx dungeon level 15 in Nethack.
2) GPT-2 language model would make random utterances from NPCs more
like talking to real person.