Maybe thou as the game is now split into 3 , will it make that much difference? add in a hard re-set with what I presume will be a limited set of choice's for your dark age .The biggest problem of the idea is that it's not a newbie friendly way. Most of newbie players don't understand what civ will be a good choice for the starting environment they faced. The traditional way - just choose the civ & leader to play and get an automatically generated map - is easier to them.
Your leader is the only the main constant choice you will need to think about .