please check out ( dungeons & dragons online the video game’s ) reincarnation system 
it added massiv replayability and player retention to that game… if i remember correctly basically when u hit max lvl u can rebirth/reincarnate & it resets u back to lvl 1 BUT the cool part is u get extra points to spend every time u do .but thay space em out so u get a point in something every rebirth but NOT a point in everything every rebirth. uumm so +to a 1stat or/1skill or/1 paragon point… it creates a almost endless progression loop that’s worth doing & i love its because i hate sitting at max lvl cap in games 
& i dont care about your seasons because i got 1 of each class & thats all im willing to make . its fine if people want to sit at max lvl but i just cant it sucks i need groth to build my toon or its just game over ZZzzZZ …& u might look at planetside2 its endless flat leveling system is the best.& id love to see blizzard make a SC MMO that’s inspired buy planetside 
IMO its the king of shooter MMOs & it needs some1 to rivel it