The key card is present but its support is thin.
Prioritize useful support such as Frontline Rush or Underfoot Underdogs.
Frontline Rush adds two bodies, improving Coordinated Maneuver and reducing Packbeast. A discounted Packbeast can be the second spell that triggers Stalwart.
Your deck already enables the plan but is losing the early turns.
Take a castable early creature or efficient answer before a second expensive payoff.
Mobilize bodies expire at the end step; use their body count while they exist. Ordinary Frontline Rush tokens remain and do not enter already attacking.
The support is missing
Favor independently useful creatures and interaction if the narrow support does not arrive.