The proposal is simple, update the old campaigns.
Why?
Because most of the civis got some changes over the years, but in the campaign the remain the same. Over the years some new units and tecs, even civ bonuses appeared. It would be cool to have them in the campaign.
New Civis.
For example, in some scenarios in the Rise of Moscow, you play ‘against’ The Golden Horde (which is the Mongols), but now we can play against them for real. Same thing, When we play against Templars, or even in the future (when they are released) in some scenarios in the English campaign when you play against Vikings.