How long would it take to get all the champions?
Let's do some approximated math.
To make things easier, this will be starting at level 30 and somehow you own no champions or BE (not possible, but I don't feel like doing the math on 1-30.)
These calculations are assuming you play 4 games a day and have exactly a 50% winrate.
Every champion combined currently costs 573000 BE, or 343800 if you unlock them via champion shard (champion shards can be turned into permanent for 60% of the cost of buying them outright)
The average game lasts 28-29 minutes, which will net you about 160 xp for a loss, or 190 xp for a win. average that to 175xp per game.
Add 400 XP for FWOTD, that's 1100 XP every day.
The average level takes 3172 xp (3057 avreage from 30-49, but again, this is just an approximation, so using 3172)
It would take 2.88 days per level, which I'm going to round to 3 to make things easier.
You gain an average of 910 BE per capsule, or 2120 BE every 10 levels for the larger capsule. Add 150 BE for fwotd and you get 1060 BE per level with 2270 every 10.
It would take you until level 322 to get the BE required to purchase every champion from a champion shard, or level 516 to buy them outright.
If you average 1 level every 3 days, that's either 876 days (2.4 years) or 1548 days (4.2 years).
The actual number is a bit less than that since I rounded up, ignored 1-30, and ignored the average for levels 30-49.
So figure it would take between 2-4 years playing 4 games a day to unlock every champion.