The AI is never going to be great. There is very little incentive for Firaxis to dedicate those resources in that way. They are a game company. Pride of craftsmanship only goes so far. At some point, you have to recognize that spending a million+ dollars (three to five person team for three years) on a feature that will not substantially increase sales or even be noticed by most of your players is bad business. We who come to fan sites and break apart games for exploits are a small minority of gamers. Take a look at the achievement stats for an idea of how differently we approach the game. Note that you can earn achievements while using mods. Less than 1% have the Scythian Horse Rush. Only 18% have won a game at all. Put a city under siege is at 32%, and found or conquer a city on another continent is at 55%.
We, the folks who learn systems and bend them to the breaking point, are not the target audience. It's not a profitable audience to target. It is also an audience that has proven itself, time and again, willing to mod what they want into a game, no matter how difficult that modding is. We did it with Civ IV (Rhye's and Fall, Fall from Heaven), we did it in Civ V (Vox Populi, Super Power, Enlightenment Era, and more), we'll do it in Civ VI. The mod scene is already hard at work picking apart what they can and transferring what was learned of Civ V into modding Civ VI.
Firaxis has promised better modding support, better modding tools, and access to important code resources in the very near future. If they can follow through on this, it is the best thing that can happen to our audience. It is also an investment that pays off, judging by other games that invest in their modding scene. It's certainly going to earn them more sales than a high-quality AI, and it is far cheaper to develop.
Another nice patch would be to make it so you can harvest the strategic and luxury resources (modded this in until they patch it). As you progress through the game, some strategic resources become obsolete as you advance through the eras, so the likes of iron, niter, coal and horses are just left sitting there not being very useful in post-information era. Luxuries, If you have a load of the same one in one spot or if they're in the way of building a district or wonder, would be convenient, and a small gold boost for harvesting it as well.
OT: Have you published this anywhere? I was thinking of doing the same today, and would love to just use yours instead ;-)