Sounds good to me. The effect of the Monument could probably be affected by the Champion's level, as well as how awesome his exploits were. (killed 3 Umberdroths, a Dragon, and level 15) would probably give more bonuses than (killed 1 umberdroth, level 20), however (killed 3 Umberdroths, a dragon, and level 20) would provide even more bonuses.
probably the primary factor would be the actual accomplishments, and then the level would add a certian percentage, or so. Like a level 10 would take points (lets say prestige) 150%. so at level 1 you would have 100% prestige for accomplishments, and at level 10 you would have 150% prestige for accomplishments, and at level 20 you would have 200% prestige for accomplishments. So that once you reach level 20 your accomplishments are worth double prestige. This affects all accomplishments, not just new ones, so do something at level 1, and at level 20 its worth twice as much. Do same thing again at level 20, and its worth the same amount (twice as much). level 30 would be 250% prestige, and so on. Although I would assume that we are having a level cap somewhere around 40, and thats only for the super-bosses, or what-not ... so the norm for a "good hero" is probably level 20. Level 21-30 would be epic, and 31-40 are godlike powers. Meh, just a possibility/suggestion. Also, each level gain would probably give a certain amount of prestige as well.
But in any event, the Hero's Monument would probably give bonuses based upon his Prestige level, his specialty, and bonus-specific quests he has completed. Complete enough animal-kill or animal-capture quests and new hunters get +x% bonus vs Animals depending on Prestige level. (for example)
Of course, a simpler system would only account level, prestige, and Class. And without a proper class system, we will just have to go by which stat is highest, or which weapon he uses, something like that. But Level, Prestige, and Specialty is the simplest approach (I think). Although it would be cool for certain quests to directly affect the monument as well. Perhaps a curse or a failed quest could penalize the monument, while protecting the city from a seige of Dire-Bears possesed by evil spirits could earn special bonuses to the Monument not based on stats but as a result of completing that specific quest.