Reason to grind

I personally feel like getting a little pop up is quite bad for me grinding hours to get a lvl 7 mastery and all of the blue essence. I hope they can make a black and gold skin for each champ when u get lvl 7 or maybe 500k mastery. This would go with the free to play style people like and it gives people a reason to play a champ for a long time and people get rewarded for the grind.