I see the rebellion (without Virus) as a grinding, prolonged war between the major powers while a lot of trade is disrupted between war zones but relatively unaffected in far reaching areas of the Imperium.
Regency of Deneb/Spinward Marches.
Zru sirkaa
Vargr Extents
Vilani Empire.
League of Antares
Gateway Protectorate
3I/4I (Core)
Grand Duchy of Wenly Ruu
Federation of Ilelish
Delphine Empire
Federation of Deabei
Glimmerift Federation
Old Expanses Commonwealth
Solomani Confederation
I have a timeline, as well. I think one could still inject virus weapons at several points. Also, possibly more than 320 fleets. Remember, Dulinor is building ships in secret. Potentially, for his former 3I fleets or extra fleets.