Managing more than 15000 SEP clients

Hi evryone,

I need an advice not a solution...

I hope that i'm not bothering you whit such demande....but this is the only SEP Expert's assembly that i know.

We Have more than 15000 client(>= 16500) managed whit 3 Manager, im in charge of changing the way we r using to manage those clients:

1st & 2nd  Manager (FR & MA) : Replication between them ON

3rd manager (LY) : have no replication partner 

3 sites(eache manager have one Site)

1domaine for all the clients

We manage severl offices in severl contrys : Morocco, France, UK, Belgium, India, Roumanie(all the offices are related whit a very very big cloud)

How can i optimez this management methode ? 

Thank you for your answers and I still available if any further informations are needed.