Getting rid of the leagues as part of the NPE never made sense to me for a few reasons.

In lower leagues the cards have far fewer abilities. Most of the abilities in the game are at gold league or higher. This provides a much simpler game play in bronze and silver. And allows learning to take place gradually.

Second you can start small and then move up if you choose. For example you can first design a Bronze deck and once you are dominating Bronze you can decide to upgrade your deck to Silver.

Finally tournaments and brawls still use the leagues and so you would keep things uniform with leagues.

Of course the challenge would be creating a new system using CP, or staked SPS or whatever before moving up.