Here is my concept for how to "improve" the season plunder pass to make it feel better, and like you are earning things as you go more so rather than it just sitting there pointlessly after you get to lvl 100 in an afternoon.
After you hit lvl 100, a new tab/page will be unlocked for it. This tab is one long bar which equates to 10 lvl's worth for the normal plunder pass. This bar will continue to earn up and renowned for it as you do things in game, once you hit the end of the bar, you will earn a 25,000 gold, and 50 doubloons reward, and the bar will reset, allowing you to work towards another reward at the end.
Now, how do we balance this to not make it be an infinite gold farm?
You are only able to get the 25k and 50 doubloons a total of 5 times a week, resetting the timer every friday.