Excellent words! I also want existing gameplay to remain intact.
So I hope that some people here stop trying to remove existing well-working units (especially knight-line) from civs just to force players to use inferior alternatives. Seeing alternative units in game should come from people preferring to use them in certain situations, not from being unable to train existing well-working units.
Also if someone has crazy ideas about alternative units, then create a mod! If enough people are interested in it, then those ideas might make it to the main game.
Here is the topic, which sparked this discussion