Hey Rob,
Mighty congrats to you for getting your wonderful Anno Domini mod out for CiV. Very impressed with your rapid progress and very excited to have the opportunity to play.
Those of us, like me, who played and loved Civ 3 Anno Domini for some many countless hours, know that you're a top modder and have no doubt created another classic. I look forward to playing this, once I get G&K that is, and I totally agree with you deciding to utilise and make the most of all possible assets and mechanics available. Mods should be all they can be.
Though I haven't taken this for a whirl yet, from a theoretical design perspective it makes very good sense to have that mid-game spearman and also to exploit the City States diplomacy mod, which seems like a very good and necessary tweak. The envoys and other units fit with the era your mod covers very well and they will offer all kinds of very welcome gameplay dynamics. Indeed, they will fill in some of the gaps that you get when there is an absence of modern era units. Not that this has ever been a problem, but it can only be a good thing to have such non-military units around.
Finally, though I've not yet had the time to explore making scenarios with CiV, I may do some time. Transposing "Hegemon! Of The Classical Greek World!" from Civ 3 to CiV is something I've thought about before. Maybe others more familiar and capable will beat me to it. Either way, and in the meantime, I'm mighty glad and grateful to you for indulging all us fans of the ancient era.