I donít get why your game is any different to mine, as long as it is installed properly it should work fine apart from the known map issue around Greece [which you just go back to a saved game and move your characters around [I got this in rtw too]. Perhaps copy and paste the rome data file into your Sparta folder then past Sparta over the top just to ensure everything vanilla is in place, I think it installs better if you unzip Sparta to a separate place before copying it into rome. It is always good to make plenty of saves!
As you have seen in the dev forum, I am learning m2 skinning [and soon modelling] so stw4 will most likely be for m2k. Also there is a classical modbase being made which Sparta will go over the top of. It will be a while before it is all done, but I would ultimately like to do a complete history of Sparta mod [historically based], if we do make that then I will be making special characters for it and of course leonidas will be in there. It will be greek based and will also allow for massive expansion and colonisation as like stw3.5 is. I will do more for the other cultures too so as to make them more immersive.