I agree and want to add some more :
manipulating the Cup draw by under leveling is a method but nothing is guarantee.
As you can see above, I won a Cup , when I was lv4, in a lv7 Cup, playing with a 1* higher quality in the final and later lost from an equal q team, having better rates and "troll" conditions.
Same happened in my main team. Won a 3lv above cup once.
So luck and a "good" day it's a part of the Cup too.
In my main team, I won enough cups and trebles so I don't care any more but if I was interest for more, I should keep for every season 3 as possible lower quality players, for many seasons.
These players must always be in contract at the end/beginning of the season.
This thing now, maybe is useful for a league draw, if there are new conditions about "quality" leagues.
Of course, with that way, you can have only 16 active players (if you want to have an extra position for a free agent or a 0T academy, for selling).