This is an excellent idea, the "Team Creation UI Updates" section.

Leveled-up cards will be able to be used as the same level or lower level.

If you combine 14 level 1 common cards to get one level 3 common card, you also get level 1 and level 2 cards because you can choose which level you want to use in Silver league without any reward reduction.

Players won't hesitate to combine cards because they don't lose any useful lower level stats.