@UpmostRook9474 I came up with some other names for this generic Eagle line that you mentioned, how about this?
War Club Runner → Axe Runner → Elite Axe Runner
The [Canoe] could replace the basic warship line for Pre-Columbian civilisations and for future Native American civilisations which will be:
Canoe → War Canoe → Sturdy War Canoe (Instead of: Galley → War Galley → Galleon).
I also came up with a new unit concept that is called the [Flare Archer) which will replace the [Trebuchet] for the Native American civilisations and other civilisations that did not use it in reality. The (Crossbowman → Arbalester) upgrade could be renamed to (Improved Archer → Expert Archer) for them as well and the unit won’t wield a crossbow.
Maybe there could be a regional unit called the [Dart Throwing Runner] for the Pre-Columbian civilisations that will use a Spear-Thrower (aka the Atlatl) and which will serve as a substitute for the [Cavalry Archer] that they don’t have access to. It could also have some kind of armor reduction ability similar to the [Obuch], but the Pre-Columbian civilisations will in turn lose their access to the Scorpion line.
The catapult line (Mangonel → Onager → Siege Onager) could still be available for the Pre-Columbian civilisations since it will probably be hard to replace them with something else.