Miller and Agius replace Jesmond Zerafa and Leonard Farrugia who led the team to two successive championships in two years.
The Valletta president revealed that Brazilian duo William Barbosa and Denni Dos Santos were confirmed as two of the foreigners and they will be joined by another three Brazilian players.
Goalkeeper Andrew Hogg will be leaving the club to move to Cyprus with his place possibly be taken by Malta international goalkeeper Justin Haber.