Louis XXIV
Le Roi Soleil

That's the best pic I could find (at least on the internet, there was a much better picture but it was in a book and I don't have a scanner)
Basically, it is a Sumerian soldier riding on this primitive chariot, throwing Javelins. The Chariot is primitive in several ways. It is bulky and slow compared to later Chariots. It is pulled by 4 Onagers (small wild Donkey) instead of the usual 2 Horses. But every great invention had a begining.
What I imagine the unit would look like is something like that pic. The Sumerian driving it could look similar to the Enkidu warrior only he would be throwing Javelins
The unit would probably fit really well as a Sumerian Unique Unit, but I need it as a early chariot available to everyone (I probably need a better name than "Early Chariot" for game purposes, but I'll take one step at a time).
I guess that's about it. Any takers?