If you do ALL the weeklies, you would need to complete 41.2 BP levels on your own which would be 2,894,500 XP needed for BP100.
In the 84 days with the first round 10K daily bonuses (840K), you would need to earn 2,054,500 XP manually or average 24,458 XP per day (every day) while completing all the weeklies. If you miss the daily bonus, you will obviously have to play more to make up that lost free XP.
Here is my breakdown. If you can play every day, it will take you no more than 2-3 rounds a day to complete BP100 by the end of S1. However, just say you can only play half the days, since you also lose the daily bonus, you now have to basically play double plus an extra round per day to make up the lost points. Someone only gaining 10K per round is going to have to play 6 rounds (3 hours per day) for 42 of the 84 days in a season to complete the Battle Pass.
Playing every day:
10K per round player = 205 rounds in 84 days (2.5 rounds per day)
15K per round player = 137 rounds in 84 days (1.7 rounds per day)
20K per round player = 103 rounds in 84 days (1.3 rounds per day)
Playing only once every 2 days (42 days out of 84):
10K per round player = 247 rounds in 42 days (5.9 rounds per day)
15K per round player = 165 rounds in 42 days (3.9 rounds per day)
20K per round player = 124 rounds in 42 days (3.0 rounds per day)
To me there is an easy fix. Reset the XP Mission every week back down to 2K but have its requirements go up quicker than they currently do. This would still make it fair for both casuals and hardcore players.