Thinking outside the box, could the following be done to increase the game timeframe to include 27BC to 727AD. Firstly three things need to be done:
1) create a Mod running from 728AUC to to 754AUC - this is the hard bit what you actually do is have it running from 28AUC to 54AUC and Descartes uses his interface modding skills to physically insert the missing 7XX

2) create a Mod running from 1AUC to 727AUC (but from a player perspective this is AD or Descartes uses his interface modding skills to physically insert AD

)
3) Someone creates on of those convertors like where you can transfer from Crusader Kings to EU - in this case it should convert seamlessly or perhaps by modding the save game file
The game plays as follows:
a) Play vanilla to the 727AUC and save
b) Apply convertor so that you can play the "Mod running from 728AUC to to 754AUC"
c) Play the Mod running from 728AUC to to 754AUC until the end ie around about 1BC
d) Apply convertor so that you can play the "Mod running from 1AUC to 727AUC"
c) Play the Mod running from 1AUC to 727AUC until the end ie around about 727AD
Would this be possible ?