It feels a bit redundant to me personally. Anything that's part of this prestige level grind could be awarded somewhere else in some other way. And there are plenty of grinds to tackle in the game. Stuff from relic weapons, to pvp, to tank mounts.

There's nothing inherently wrong with the suggestion I'll add, it would be perfectly fine if they added an extra progression bar that unlocks at 80 and gives cosmetic stuff for grinding I guess. But at the same time they could equally just put that stuff in other areas and it would functionally be the same.