The Gloria seems a lot of text to set in one piece… Vivaldi (in one of my favourite works) just set the Gloria, divided into twelve sections.
Clearly this is not going to be a requiem mass – I want it to be a joyful thanksgiving. A full setting of the ordinarium (missa tota) would comprise the Kyrie, Gloria, Credo, Sanctus & Benedictus and Agnus Dei. A short mass (missa brevis) may only set the Kyrie and the Gloria. Kyrie-Gloria settings were acceptable in Roman Catholic and Protestant Churches (including the Lutheran Church) in the 18th century – the period during which West Gallery music was at its height in this country.
Decision made. (Although, knowing me, I might change my mind.) I will try to set the Kyrie and the Gloria… but will subdivide the gloria into different sections.