Can we fit the player-strength coefficient instead of hand-setting it? (No)

The player-composite differential is the lineup-aware team-strength signal the improvements roadmap §2.3 flags as the highest-leverage item in the literature. Today it enters the model only as a hand-set multiplicative log-rate offset ("Model 16"): for a fixture, Δ = α · (composite_home − composite_away) is added to home log-λ (and subtracted from away log-λ), with the single coefficient α = 0.05 chosen by the coarse 5-point grid {0, 0.005, 0.01, 0.02, 0.05}…