I think you got it.

The limit on fans would be determined by the amount of fans you have depending on the cards you have. If you had all Legend cards, You would have more fans thn you would with a mixed deck of Legend Epic and rare.

The suggestion is to limit the amount of cards than can be used. Even Clove won't have 100K legend cards.
If two players have 100K cards. and both players have all legend cards. Then yes they would earn the same roughly. Different Legend cards have varying fans.
The same for skill needed to combat ego.

If a player reached that amount of cards all Legend. It is worth their while to sell any future legends gained from packs.

But I think it works good for the long term prospects.