Unless you abuse smithing, or spend the early game just doing quests, most notables will only ever have ~0 relationship with the player. This makes this sub-system less than impactful. Notables should have more things boost their relationship, even if only a small amount each instance, so this actually matters.
Ideas:
Killing bandit parties raises relationship with notable in the nearest settlement (Any or any non-criminal. Already a popular mod)
Repeat customer (any)
Tournament winner (any, but could favor criminal since they'd have a stake in betting)
Selling merchandise needed for town's output in that town (merchant type notables)
These would only raise relationship by a small amount (1 or 2 each time), but occur often enough in normal gameplay
Ideas:
Killing bandit parties raises relationship with notable in the nearest settlement (Any or any non-criminal. Already a popular mod)
Repeat customer (any)
Tournament winner (any, but could favor criminal since they'd have a stake in betting)
Selling merchandise needed for town's output in that town (merchant type notables)
These would only raise relationship by a small amount (1 or 2 each time), but occur often enough in normal gameplay