I know about all the controversy about Gift of battle for Legendaries and all that, but try to stay on topic please
So this idea is pretty simple. World completion would be separated by regions into 5 reward tracks. Each track is locked until the previous one is completed. The last track rewards 1 Gift of Exploration instead of 2 that you would get from Mapping. They will not reward the gold star by a characters name, the title "Been there, Done That" or any AP, and would not complete any hearts or unlock waypoints . Once all tracks are completed, they can be restarted, from the beginning. This would only be for core maps and first generation Legendaries.
1st Tier-Ascalon Reward Track-Standard Rewards
2nd Tier- Shiverpeaks Reward Track-Standard Rewards (Locked until Ascalon is completed)
3rd Tier- Maguuma Reward Track- Standard Rewards (Locked until Shiverpeaks is completed)
4th Tier- Kryta Reward Track- Standard Rewards (Locked until Maguuma is completed)
5th Tier- Orr Reward Track- Gift of Exploration (Locked until Kryta is completed)
It takes on average around 8 hours with boosts to complete a reward track, so it would take around 40 hours to complete it in total for 1 gift of exploration which is half of what you would get for World Completion. I think time wise it is about on par with how long you would spend doing this in PvE, however with less rewards.
Somewhere chasing bags....