I think if we keep nerfing Bronze rewards, we will get less new player retention.
Instead I propose this to encourage players to have skin in the game.
make it so any player with less then 1000 SPS staked, treat all their cards as "Soul Bound"
Make it so they cant sell those cards, trade those cards, or delegate those cards. until they have 1000 SPS staked.
No one who plays for more than a season or several should really be in bronze for that long anyway. That's how I feel, anyway. It's not that hard to climb up to Silver at least.