The only way I could see Warlock patrons playing a bigger role than just popping in to offer advice or support here and there is if they enact a system like the Paladin's oath where Tav is obliged to choose certain RP actions. However, instead of vague guidelines for behavior like an oath, Tav's Patron would pop into their head with very specific orders. Do as they say *or face the consequences*.
example:
NPC: Hello, I need your help with something.
Tav: Hi, what is it?
NPC: Can you go over to the ruined village and collect my family's hierlooms for me?
Fiend Patron (in Tav's mind): This dude is going to ruin my plans. Kill him. Or else.
