Isn’t that what Chronicles does, just slowly.
Porting over civs to AoE2 is basically like making a new civ since the game is totally different. AoE1 and AoE2 Romans are completely different, they don’t even have similar civ bonuses.
But I think they should port all AoE1 units to Chronicles because why not? The assets are already made and they fit into the setting.
Though I did make a tread about How to add the AoE1 civilsiations to AoE2 for unranked
That was before Chronicles, now my suggestions would probably look a little different and include some Chronicles things.