SBC Idea for Untradeable Promo Cards

I have an idea to increase sales of untradeable guaranteed promo packs that will also give players a more valuable outlet to user their promo fodder cards on.

Some promos like Unbreakables and Fantasy are not exciting so fewer people buy the guaranteed store packs. But what if you create an incentive for people to buy these packs because it would give them progress towards a card they actually want? Create an SBC that never expires. The sbc requires x-number of 86 level squads of any untradeable card that is a promo. The SBC rewards you with a token. Then the player can use that token to trade for a special edition card. The card would be rotated out to keep pace with the meta, but the SBC will stay open so players can keep adding to it as they unlock cards from promos. The special edition card should not be available from packs, otherwise if you unlock this card from a pack you'd feel like you just wasted your time on the SBC.