I think the solution of offering some of the Ranked currency that increase based on Rank is great for the Augmented weapons.

As for the overall lackluster rewards for higher ranks or even Top 100, they could easily just use a color swap of the Series Armor set or Mount, whichever there currently is on the ongoing one.

That way, there would be some prestige in playing but something similar would be avaiable for everyone. Imagine having the Archfiend set from first season with blue or green bits instead of red as example for high end reward.