Many things in this game that take a considerable time to complete have little to no benefit. Things like completing a maps main and side missions, unlocking all lookouts/outposts, discovering all the codex entries, and building all the hunting structures have essentially no incentive. Changing this would be awesome for the game as it would add some more depth to the progression system and entice players to do more than just hunt (just hunting isn’t bad, but this game has more to offer than just hunting animals).
Here are my suggestions:
Completion of the maps main and side missions grants you a 10% increase in the cash earned from harvested animals on that map.
Unlocking all lookouts/outposts on the map grants you a 10% reduction in the cost of changing time on that map.
Unlocking all codex entries and building all hunting structures grants you a 10% buff to xp and weapon score from harvested animals on that reserve.
Don’t take this next one too seriously
Completing all of the above will grant you 1 additional perk/skill point(you choose which one).
This means that for every map release you have the opportunity to gain an additional perk/skill point once you “complete” the map.