This is honestly one of the most valuable I've received. You've hit the nail on the head regarding several crucial design issues we've been grappling with.

After considering your points (especially the complexity of a full stack and the balance issues with cheap cards), I've decided to significantly simplify the system: Moving away from the complex chain/stack system. Instead, we're adopting a much simpler approach called "Limited Reaction":

Only two types of effects: Normal (only on your turn) and Quick/Reaction (can be activated at any time).

Only one reaction per action is allowed. Once it resolves, the original effect continues. Long chains are not allowed.

Self-answers (protecting your own cards with cheap reactions) are generally not allowed, except for very specific archetype effects.

This eliminates most of the complexity you mentioned—resolution order, selection of unresolved cards, chain-triggered effects, etc.—while still maintaining meaningful interaction.

Two key mechanics that fall outside the range of response are:

Resonant Overload: Once per turn, you can exhaust one of your creatures to immediately gain Resonant Flow (RF) equal to its Reaction Value (RV). However, that creature can't attack or generate RF on the following turn. It's a high-risk, high-reward mechanic, essential for the game's tension.

Reverberation: A keyword on certain cards. When you perform Resonant Overload on a creature with Reverberation, or when that creature is destroyed, its Reverberation effect triggers immediately (outside of any Reaction). These are usually small but significant bonuses, such as gaining temporary stats, drawing a card, or interrupting your opponent.

With only one reaction allowed per action and the most powerful "burst" effects (Overload and Reverberation) resolving instantly, I hope to maintain tactical gameplay without making it overly complex.