Part of the problem is that converting Civ 4 models to Civ 5 is NOT a "simple conversion". I don't really understand much about the process myself, but from the discussions I've seen people have in the forums, the conversion process appears to require the model to practically be rebuilt from scratch. There's also a very limited number of people working in that area -- many of the people who contributed the earlier models don't seem to post as often, and even fewer people are working on any fantasy models. (The most recent models date back to November and August.) What's more, with it being the holiday season, it's likely many of the people involved simply have other real life demands on their time, and don't have much to devote towards dabbling with Civ mods.
In the end, I suspect if you really want to get this done, you will likely have to learn to do it yourself. From what I've seen, wolfdog's tutorial on the conversion process has been helpful for some people to start learning how to convert models; it may be something to look into.