For my first scenario mod, I am modding the Rise of Rome scenario. I gave each civ an extra trait. (Four for the original civs, three four the original NPCs.) I made the previously-NPC civs playable and gave them an Army in their capitals. I added an eighth luxury, wool, but I can't figure out how quite yet to get the wool art from the medieval scenario into this one (am using rubber as a stand-in for now).
I have gold and silver as resources. They display fine enough. I have the units added in that I wanted to add in. At least I hope. Haven't tried building any of them.
I have the techs added, even though they are a little messy.
I have a lot of wonders, small and great, added in and modded.
None of these have civilopedia entries, except a few units and the wonders which to not break the game have one, but not linked in the way I was expecting/hoping them to.
I think, as is, with me as the creator knowing all the changes I made, it's playable (as long as I didn't crash the game).
But it sure as heck isn't in any way shape or form. Good. Not yet anyway. I'll give it a few test-runs (I can do at least 8!), to see if I can have it work for me the way I am envisioning it to work.
That may seem like it's lousy.
But this was much, much further than I was expecting to get!