Maybe email it to Gabe as a suggestion since he likes getting emails from random gamers.
gaben@valvesoftware.com
Let me know if you get put in so I can complain about it being an OP character played by scrubs and tryhards, and should be nerves for balance
For a while dota 2 had a pve roguelike game mode that was legitimately pretty fun, though valve keeps doing this thing where they make the fun temporary mode ballbustingly hard which I think kinda kills it for the majority of players
I don't foresee a single player game mode tbh but I think finding ways to tell a personal story across your many matches of a multiplayer pvp game is unexplored territory that valve could break new ground in. Maybe a hub similar to games like Hades, with NPCs who have comments about wins and losses or particular feats you pulled off.