Why don't start adding features to avoid that horribly title "AoE Clone" but at last that title now is for Empires Apart.
Secondary attack.
Dock give some territorial bonus
New building that's no depend of territory but can be easily to rush.
Minifaction design or layout
Capture units
More variety and counters
Mercenary system.
Slave system
New minimap features
Diplomacy features like trade units between players.
New relic types
More nomad styles like scattered unit over the map.
More mission maps
Add objectives