AOE4 must have an offline campaign like AOE3 and Online feature like AOEO
Regarding the online gameplay where users can buy it like a DLC. We can do quests as co op or alone.
Online multiplayer PvP can be accessible for the non DLC buyer too.
The AOE4O will have
Colonial Era ,
World Wars (1910-20 , 1930-1945),
Cold War (1950 - 70, 70-90) and
Modern age scenario (1990- now)
The scenarios will appear like Regional specific Colonial and world wars
Cold War will be like Argos
Modern age will be like Cyprus (AOEO users will know )
cold war and modern age games will be like competing with the AI and have independent allies, Resource tribute to them to become client or subjugation of them by converting their government centre. We could have the common trade route like AOE3. Failure to protect our ally from territorial loss skirmish will make us lose them to the other side. Spies can indulge in conversion activities after research. Instead converting enemy building garrisoning spies will render them unproductive and give map reveal of the building LoS.
We can work on our allies resource mines, farm buildings but not with full resource but for passive trickle of revenue. The rest of engagement will be direct with the enemy like previous AOE.
North America, British commonwealth, Europe West(France, Spain, Belgium, Italy Turkey combined), Germany (East Europe) , Russia Motherland (Soviet Bloc) , China, Japan These will be full civilizations
Pro civilization like India, Africa North(Egypt), Africa South (Zulu) , Latin America, South east asia and Oceania
these civs will have access to coldwar and modern age campaigns