Hmm. I didn't think this would be a roadblock. I'd like to know how to do this, too.
A possible workaround: Maybe you could lay out starting points and resources in such a way that AI will have to build cities in your chosen locations. (Hope the AI is smart enough to do that.) Problem there is you won't be able to name the cities.
Or, if the city location is only for decorative/narrative--and not strategic--purposes, you could just make custom tiles to stand in for cities.