It might be helpful to include some references to the Satsai, as Swaminarayan's teachings are in that text. Also, the significance of daily rituals and how Mahapuja is a more elaborate form of daily pujas.
Also, the role of Mahant and other priests in conducting the ritual. Their attire, the use of specific instruments like drums (damru), and singing mantras. The community participation is important too—devotees might offer items, donate, or attend the pujas. baps mahapuja vidhi pdf
I should also mention the spiritual benefits according to BAPS beliefs, like receiving the deity's blessings, purification, and fulfillment of desires. Maybe touch on the concept of Bhakti (devotion) being central to the Mahapuja. It might be helpful to include some references